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Bad chip?

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  • wfahle
    I m running the tests for the tx opamp stage of a tx/rx ensemble build, per the instructions at http://www.wb5rvz.com/sdr/ensemble/08_tx_opamp.htm Everything
    Message 1 of 28 , Oct 30, 2012
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      I'm running the tests for the tx opamp stage of a tx/rx ensemble build, per the instructions at http://www.wb5rvz.com/sdr/ensemble/08_tx_opamp.htm
      Everything checks out fine except for 2 voltages. Pin 1 of U6 is reading 5 volts instead of 2.5, and pin 7 of that same chip is reading near 0, instead of 2.5. This is unbridged, with or without the USB connected, with power.

      It has passed all prior tests, including receiving a signal in CW over the air. I have continuity-tested every pin of both chips U6 and U7 to make sure each pin connects to each solder joint, and I have checked that no pin shorts to any other pin, except pin 3 to pin 5 on both chips, as they should. Pin 1 to Pin 6 shows 10k resistance, as it should, on both chips. I have double-checked the value of every resistor in the TX circuit. I even pulled R21 to do a direct measure because it was reading about half its actual value plugged in. Pulled it read 2.21k as expected. Pin 1 and 7 of U7 both read correct values of 2.5 volts. So my question is, do I have a bad chip? Something else I can check?

      The voltage to R23 hairpin is 2.5, as is R15 and R16, R24, R22, R21, R20, R19 and R18. Only R17 reads 5 volts. I can't see how it is coming anywhere but from the chip.

      R25 is -1.2, R26 is 2.5, R27 is 2.5, and R28 is 1.6. The weirdest one there is R25, so I checked the other side of it and it reads -.9. The last chip is uninstalled at this point, but I'm not sure where the negative voltage is coming from.
    • wfahle
      Pictures of relevant part of board: http://imgur.com/a/BFFoj
      Message 2 of 28 , Oct 30, 2012
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        Pictures of relevant part of board:
        http://imgur.com/a/BFFoj

        --- In softrock40@yahoogroups.com, "wfahle" <billfahle@...> wrote:
        >
        > I'm running the tests for the tx opamp stage of a tx/rx ensemble build, per the instructions at http://www.wb5rvz.com/sdr/ensemble/08_tx_opamp.htm
        > Everything checks out fine except for 2 voltages. Pin 1 of U6 is reading 5 volts instead of 2.5, and pin 7 of that same chip is reading near 0, instead of 2.5. This is unbridged, with or without the USB connected, with power.
        >
        > It has passed all prior tests, including receiving a signal in CW over the air. I have continuity-tested every pin of both chips U6 and U7 to make sure each pin connects to each solder joint, and I have checked that no pin shorts to any other pin, except pin 3 to pin 5 on both chips, as they should. Pin 1 to Pin 6 shows 10k resistance, as it should, on both chips. I have double-checked the value of every resistor in the TX circuit. I even pulled R21 to do a direct measure because it was reading about half its actual value plugged in. Pulled it read 2.21k as expected. Pin 1 and 7 of U7 both read correct values of 2.5 volts. So my question is, do I have a bad chip? Something else I can check?
        >
        > The voltage to R23 hairpin is 2.5, as is R15 and R16, R24, R22, R21, R20, R19 and R18. Only R17 reads 5 volts. I can't see how it is coming anywhere but from the chip.
        >
        > R25 is -1.2, R26 is 2.5, R27 is 2.5, and R28 is 1.6. The weirdest one there is R25, so I checked the other side of it and it reads -.9. The last chip is uninstalled at this point, but I'm not sure where the negative voltage is coming from.
        >
      • Alan
        ... Subject: [softrock40] Bad chip? ... Where have you got the meter negative clip? 73 Alan G4ZFQ
        Message 3 of 28 , Oct 30, 2012
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          ----- Original Message -----
          Subject: [softrock40] Bad chip?


          > I'm running the tests for the tx opamp stage of a tx/rx ensemble build, per the instructions at
          > http://www.wb5rvz.com/sdr/ensemble/08_tx_opamp.htm
          > Everything checks out fine except for 2 voltages. Pin 1 of U6 is reading 5 volts instead of 2.5, and pin 7 of that same chip is
          > reading near 0, instead of 2.5. This is unbridged, with or without the USB connected, with power.
          >
          > It has passed all prior tests, including receiving a signal in CW over the air. I have continuity-tested every pin of both chips
          > U6 and U7 to make sure each pin connects to each solder joint, and I have checked that no pin shorts to any other pin, except pin
          > 3 to pin 5 on both chips, as they should. Pin 1 to Pin 6 shows 10k resistance, as it should, on both chips. I have double-checked
          > the value of every resistor in the TX circuit. I even pulled R21 to do a direct measure because it was reading about half its
          > actual value plugged in. Pulled it read 2.21k as expected. Pin 1 and 7 of U7 both read correct values of 2.5 volts. So my question
          > is, do I have a bad chip? Something else I can check?
          >
          > The voltage to R23 hairpin is 2.5, as is R15 and R16, R24, R22, R21, R20, R19 and R18. Only R17 reads 5 volts. I can't see how it
          > is coming anywhere but from the chip.
          >
          > R25 is -1.2, R26 is 2.5, R27 is 2.5, and R28 is 1.6. The weirdest one there is R25, so I checked the other side of it and it
          > reads -.9. The last chip is uninstalled at this point, but I'm not sure where the negative voltage is coming from.
          >
          >

          Where have you got the meter negative clip?

          73 Alan G4ZFQ
        • wfahle
          On R50 Hairpin (the standard regular ground reference from the power supply stage).
          Message 4 of 28 , Oct 30, 2012
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            On R50 Hairpin (the standard regular ground reference from the power supply stage).

            --- In softrock40@yahoogroups.com, "Alan" <alan4alan@...> wrote:
            >
            >
            > ----- Original Message -----
            > Subject: [softrock40] Bad chip?
            >
            >
            > > I'm running the tests for the tx opamp stage of a tx/rx ensemble build, per the instructions at
            > > http://www.wb5rvz.com/sdr/ensemble/08_tx_opamp.htm
            > > Everything checks out fine except for 2 voltages. Pin 1 of U6 is reading 5 volts instead of 2.5, and pin 7 of that same chip is
            > > reading near 0, instead of 2.5. This is unbridged, with or without the USB connected, with power.
            > >
            > > It has passed all prior tests, including receiving a signal in CW over the air. I have continuity-tested every pin of both chips
            > > U6 and U7 to make sure each pin connects to each solder joint, and I have checked that no pin shorts to any other pin, except pin
            > > 3 to pin 5 on both chips, as they should. Pin 1 to Pin 6 shows 10k resistance, as it should, on both chips. I have double-checked
            > > the value of every resistor in the TX circuit. I even pulled R21 to do a direct measure because it was reading about half its
            > > actual value plugged in. Pulled it read 2.21k as expected. Pin 1 and 7 of U7 both read correct values of 2.5 volts. So my question
            > > is, do I have a bad chip? Something else I can check?
            > >
            > > The voltage to R23 hairpin is 2.5, as is R15 and R16, R24, R22, R21, R20, R19 and R18. Only R17 reads 5 volts. I can't see how it
            > > is coming anywhere but from the chip.
            > >
            > > R25 is -1.2, R26 is 2.5, R27 is 2.5, and R28 is 1.6. The weirdest one there is R25, so I checked the other side of it and it
            > > reads -.9. The last chip is uninstalled at this point, but I'm not sure where the negative voltage is coming from.
            > >
            > >
            >
            > Where have you got the meter negative clip?
            >
            > 73 Alan G4ZFQ
            >
          • Alan
            ... Subject: [softrock40] Re: Bad chip? ... Right, maybe the voltage is coming through the mixer with some sort of diode action. ... This could be the IC, but
            Message 5 of 28 , Oct 30, 2012
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              ----- Original Message -----
              Subject: [softrock40] Re: Bad chip?


              > On R50 Hairpin (the standard regular ground reference from the power supply stage).
              >

              Right, maybe the voltage is coming through the mixer with some sort of diode action.


              >> > Everything checks out fine except for 2 voltages. Pin 1 of U6 is reading 5 volts instead of 2.5,

              This could be the IC, but look for a possible PCB fault, a whisker shorting to 5V.
              But presumably pins 2,3 are 2V5? Why is 5V not sent to pin 2 via R16? Check R16 and soldering.

              73 Alan G4ZFQ



              and pin 7 of that same chip is
              >> > reading near 0, instead of 2.5. This is unbridged, with or without the USB connected, with power.
              >> >
              >> > It has passed all prior tests, including receiving a signal in CW over the air. I have continuity-tested every pin of both
              >> > chips
              >> > U6 and U7 to make sure each pin connects to each solder joint, and I have checked that no pin shorts to any other pin, except
              >> > pin
              >> > 3 to pin 5 on both chips, as they should. Pin 1 to Pin 6 shows 10k resistance, as it should, on both chips. I have
              >> > double-checked
              >> > the value of every resistor in the TX circuit. I even pulled R21 to do a direct measure because it was reading about half its
              >> > actual value plugged in. Pulled it read 2.21k as expected. Pin 1 and 7 of U7 both read correct values of 2.5 volts. So my
              >> > question
              >> > is, do I have a bad chip? Something else I can check?
              >> >
              >> > The voltage to R23 hairpin is 2.5, as is R15 and R16, R24, R22, R21, R20, R19 and R18. Only R17 reads 5 volts. I can't see how
              >> > it
              >> > is coming anywhere but from the chip.
              >> >
              >> > R25 is -1.2, R26 is 2.5, R27 is 2.5, and R28 is 1.6. The weirdest one there is R25, so I checked the other side of it and it
              >> > reads -.9. The last chip is uninstalled at this point, but I'm not sure where the negative voltage is coming from.
              >> >
              >> >
              >>
              >> Where have you got the meter negative clip?
              >>
              >> 73 Alan G4ZFQ
              >>
              >
              >
              >
              >
              > ------------------------------------
              >
              > Yahoo! Groups Links
              >
              >
              >
            • wfahle
              Ok, I pulled R16, and it still reads 5v at pin 1. R16 measures out at 10k as it should, but with it pulled there is very little voltage at pin 2. The current,
              Message 6 of 28 , Oct 30, 2012
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                Ok, I pulled R16, and it still reads 5v at pin 1. R16 measures out at 10k as it should, but with it pulled there is very little voltage at pin 2. The current, since I can now measure it, across R16 is .24mA. The votage at pin 7 doesn't change either; it's still almost zero. The others besides 2 are unchanged. Pin 2 goes almost to zero vs. the 2.5 it had been reading. I guess R16 becomes part of a voltage divider under the circumstances; I don't understand circuits this complex. So I will try to unseat U6 and see if there is a solder bridge under it from 1 to 8 or something (they are across from each other).

                --- In softrock40@yahoogroups.com, "Alan" <alan4alan@...> wrote:
                >
                >
                > ----- Original Message -----
                > Subject: [softrock40] Re: Bad chip?
                >
                >
                > > On R50 Hairpin (the standard regular ground reference from the power supply stage).
                > >
                >
                > Right, maybe the voltage is coming through the mixer with some sort of diode action.
                >
                >
                > >> > Everything checks out fine except for 2 voltages. Pin 1 of U6 is reading 5 volts instead of 2.5,
                >
                > This could be the IC, but look for a possible PCB fault, a whisker shorting to 5V.
                > But presumably pins 2,3 are 2V5? Why is 5V not sent to pin 2 via R16? Check R16 and soldering.
                >
                > 73 Alan G4ZFQ
                >
                >
                >
                > and pin 7 of that same chip is
                > >> > reading near 0, instead of 2.5. This is unbridged, with or without the USB connected, with power.
                > >> >
                > >> > It has passed all prior tests, including receiving a signal in CW over the air. I have continuity-tested every pin of both
                > >> > chips
                > >> > U6 and U7 to make sure each pin connects to each solder joint, and I have checked that no pin shorts to any other pin, except
                > >> > pin
                > >> > 3 to pin 5 on both chips, as they should. Pin 1 to Pin 6 shows 10k resistance, as it should, on both chips. I have
                > >> > double-checked
                > >> > the value of every resistor in the TX circuit. I even pulled R21 to do a direct measure because it was reading about half its
                > >> > actual value plugged in. Pulled it read 2.21k as expected. Pin 1 and 7 of U7 both read correct values of 2.5 volts. So my
                > >> > question
                > >> > is, do I have a bad chip? Something else I can check?
                > >> >
                > >> > The voltage to R23 hairpin is 2.5, as is R15 and R16, R24, R22, R21, R20, R19 and R18. Only R17 reads 5 volts. I can't see how
                > >> > it
                > >> > is coming anywhere but from the chip.
                > >> >
                > >> > R25 is -1.2, R26 is 2.5, R27 is 2.5, and R28 is 1.6. The weirdest one there is R25, so I checked the other side of it and it
                > >> > reads -.9. The last chip is uninstalled at this point, but I'm not sure where the negative voltage is coming from.
                > >> >
                > >> >
                > >>
                > >> Where have you got the meter negative clip?
                > >>
                > >> 73 Alan G4ZFQ
                > >>
                > >
                > >
                > >
                > >
                > > ------------------------------------
                > >
                > > Yahoo! Groups Links
                > >
                > >
                > >
                >
              • wfahle
                Well NOW it s the chip for sure. In an attempt to remove the IC to check voltages and such, the green covering began to burn through exposing the copper traces
                Message 7 of 28 , Oct 31, 2012
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                  Well NOW it's the chip for sure. In an attempt to remove the IC to check voltages and such, the green covering began to burn through exposing the copper traces beneath. So I got out the clippers and clipped it loose from the board, so that I could remove each lead individually. This worked, but it tore up some of the pads in the process. I intend to replace it with this chip because it is available locally (and I don't think going SMT again is going to make life any easier):
                  http://www.nteinc.com/specs/700to799/pdf/nte778a.pdf

                  --- In softrock40@yahoogroups.com, "wfahle" <billfahle@...> wrote:
                  >
                  > Ok, I pulled R16, and it still reads 5v at pin 1. R16 measures out at 10k as it should, but with it pulled there is very little voltage at pin 2. The current, since I can now measure it, across R16 is .24mA. The votage at pin 7 doesn't change either; it's still almost zero. The others besides 2 are unchanged. Pin 2 goes almost to zero vs. the 2.5 it had been reading. I guess R16 becomes part of a voltage divider under the circumstances; I don't understand circuits this complex. So I will try to unseat U6 and see if there is a solder bridge under it from 1 to 8 or something (they are across from each other).
                  >
                  > --- In softrock40@yahoogroups.com, "Alan" <alan4alan@> wrote:
                  > >
                  > >
                  > > ----- Original Message -----
                  > > Subject: [softrock40] Re: Bad chip?
                  > >
                  > >
                  > > > On R50 Hairpin (the standard regular ground reference from the power supply stage).
                  > > >
                  > >
                  > > Right, maybe the voltage is coming through the mixer with some sort of diode action.
                  > >
                  > >
                  > > >> > Everything checks out fine except for 2 voltages. Pin 1 of U6 is reading 5 volts instead of 2.5,
                  > >
                  > > This could be the IC, but look for a possible PCB fault, a whisker shorting to 5V.
                  > > But presumably pins 2,3 are 2V5? Why is 5V not sent to pin 2 via R16? Check R16 and soldering.
                  > >
                  > > 73 Alan G4ZFQ
                  > >
                  > >
                  > >
                  > > and pin 7 of that same chip is
                  > > >> > reading near 0, instead of 2.5. This is unbridged, with or without the USB connected, with power.
                  > > >> >
                  > > >> > It has passed all prior tests, including receiving a signal in CW over the air. I have continuity-tested every pin of both
                  > > >> > chips
                  > > >> > U6 and U7 to make sure each pin connects to each solder joint, and I have checked that no pin shorts to any other pin, except
                  > > >> > pin
                  > > >> > 3 to pin 5 on both chips, as they should. Pin 1 to Pin 6 shows 10k resistance, as it should, on both chips. I have
                  > > >> > double-checked
                  > > >> > the value of every resistor in the TX circuit. I even pulled R21 to do a direct measure because it was reading about half its
                  > > >> > actual value plugged in. Pulled it read 2.21k as expected. Pin 1 and 7 of U7 both read correct values of 2.5 volts. So my
                  > > >> > question
                  > > >> > is, do I have a bad chip? Something else I can check?
                  > > >> >
                  > > >> > The voltage to R23 hairpin is 2.5, as is R15 and R16, R24, R22, R21, R20, R19 and R18. Only R17 reads 5 volts. I can't see how
                  > > >> > it
                  > > >> > is coming anywhere but from the chip.
                  > > >> >
                  > > >> > R25 is -1.2, R26 is 2.5, R27 is 2.5, and R28 is 1.6. The weirdest one there is R25, so I checked the other side of it and it
                  > > >> > reads -.9. The last chip is uninstalled at this point, but I'm not sure where the negative voltage is coming from.
                  > > >> >
                  > > >> >
                  > > >>
                  > > >> Where have you got the meter negative clip?
                  > > >>
                  > > >> 73 Alan G4ZFQ
                  > > >>
                  > > >
                  > > >
                  > > >
                  > > >
                  > > > ------------------------------------
                  > > >
                  > > > Yahoo! Groups Links
                  > > >
                  > > >
                  > > >
                  > >
                  >
                • MICHAEL TALLENT
                  You really want a low noise op-amp for this application as it will determine the noise floor of your receiver. The data sheet you linked looks like nothing
                  Message 8 of 28 , Oct 31, 2012
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                    You really want a low noise op-amp for this application as it will determine
                    the noise floor of your receiver. The data sheet you linked looks like
                    nothing special, so you will not get the performance that these receivers
                    are capable of.

                    Mike T W6MXV

                    ----- Original Message -----
                    From: "wfahle" <billfahle@...>
                    To: <softrock40@yahoogroups.com>
                    Sent: Wednesday, October 31, 2012 12:31 PM
                    Subject: [softrock40] Re: Bad chip?


                    > Well NOW it's the chip for sure. In an attempt to remove the IC to check
                    > voltages and such, the green covering began to burn through exposing the
                    > copper traces beneath. So I got out the clippers and clipped it loose from
                    > the board, so that I could remove each lead individually. This worked, but
                    > it tore up some of the pads in the process. I intend to replace it with
                    > this chip because it is available locally (and I don't think going SMT
                    > again is going to make life any easier):
                    > http://www.nteinc.com/specs/700to799/pdf/nte778a.pdf
                    >
                    > --- In softrock40@yahoogroups.com, "wfahle" <billfahle@...> wrote:
                    >>
                    >> Ok, I pulled R16, and it still reads 5v at pin 1. R16 measures out at 10k
                    >> as it should, but with it pulled there is very little voltage at pin 2.
                    >> The current, since I can now measure it, across R16 is .24mA. The votage
                    >> at pin 7 doesn't change either; it's still almost zero. The others
                    >> besides 2 are unchanged. Pin 2 goes almost to zero vs. the 2.5 it had
                    >> been reading. I guess R16 becomes part of a voltage divider under the
                    >> circumstances; I don't understand circuits this complex. So I will try to
                    >> unseat U6 and see if there is a solder bridge under it from 1 to 8 or
                    >> something (they are across from each other).
                  • warrenallgyer
                    Bill I feel your pain.... been there, done that... more than once in fact. A trick that will not help you now but may in the future: When removing multi-pin
                    Message 9 of 28 , Oct 31, 2012
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                      Bill

                      I feel your pain.... been there, done that... more than once in fact.

                      A trick that will not help you now but may in the future: When removing multi-pin SMT devices I first solder all the pins together, using as little solder as possible. Then, when you apply the iron it can loosen one complete side at the same time. Carefully bending the chip up with needle nose applied to the ends will free this side. Then do the same on the other side and the chip comes up with minimal damage. Solderwick will clean up the lands and you are ready to install a replacement.

                      After many many lands lifted and chips destroyed (I am a slow-learner) this trick has saved the day many times.

                      Good luck to you.

                      Warren Allgyer - W8TOD

                      --- In softrock40@yahoogroups.com, "wfahle" <billfahle@...> wrote:
                      >
                      > Well NOW it's the chip for sure. In an attempt to remove the IC to check voltages and such, the green covering began to burn through exposing the copper traces beneath. So I got out the clippers and clipped it loose from the board, so that I could remove each lead individually. This worked, but it tore up some of the pads in the process. I intend to replace it with this chip because it is available locally (and I don't think going SMT again is going to make life any easier):
                    • Patrick Hall
                      Interesting technique.    What I do is to remove as much solder as I can with solder wick, then hold the chip with pliers while I blast it with a heat gun. 
                      Message 10 of 28 , Oct 31, 2012
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                        Interesting technique. 
                         
                        What I do is to remove as much solder as I can with solder wick, then hold the chip with pliers while I blast it with a heat gun.  After a minute or so the chip will gently lift off with no bent leads and no lifted pads.  Easy - if you have a heat gun that will go high enough to melt solder. 
                         
                        Patrick KF7UJM

                        From: warrenallgyer <allgyer@...>
                        To: softrock40@yahoogroups.com
                        Sent: Wednesday, October 31, 2012 4:16 PM
                        Subject: [softrock40] Re: Bad chip?
                         
                        Bill

                        I feel your pain.... been there, done that... more than once in fact.

                        A trick that will not help you now but may in the future: When removing multi-pin SMT devices I first solder all the pins together, using as little solder as possible. Then, when you apply the iron it can loosen one complete side at the same time. Carefully bending the chip up with needle nose applied to the ends will free this side. Then do the same on the other side and the chip comes up with minimal damage. Solderwick will clean up the lands and you are ready to install a replacement.

                        After many many lands lifted and chips destroyed (I am a slow-learner) this trick has saved the day many times.

                        Good luck to you.

                        Warren Allgyer - W8TOD

                        --- In mailto:softrock40%40yahoogroups.com, "wfahle" <billfahle@...> wrote:
                        >
                        > Well NOW it's the chip for sure. In an attempt to remove the IC to check voltages and such, the green covering began to burn through exposing the copper traces beneath. So I got out the clippers and clipped it loose from the board, so that I could remove each lead individually. This worked, but it tore up some of the pads in the process. I intend to replace it with this chip because it is available locally (and I don't think going SMT again is going to make life any easier):

                      • Lawrence Galea
                        Another trick is to tread a thin insulated wire or a wire which does not take solder easily under the pins on one side, solder the end of the wire to a
                        Message 11 of 28 , Nov 1, 2012
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                          Another trick is to tread a thin insulated wire or a wire which does not take solder easily under the pins on one side, solder the end of the wire to a suitable solder pad near one side of the chip, then heat the pins one by one starting from the one farthest away from where you soldered the wire to the solder pad and when the solder melts pull the wire under the pin. This will push up the pin from the pcb. Do all the pins on one side and them to the other side.
                          Regards
                          Lawrence
                                                        Chip pins
                                                               ----------------
                           Solder pad  0-------------------------------------------------------Wire
                                                               |                      |
                                                                   Chip
                                                               ----------------

                          Hope this explains.
                          0 is solder pad where wire is soldered
                          First heat the pin from the right hand side on the diagram and when solder melts pull the wire under the pin to the top of the page in this diagram and move towards the left pin by pin.
                          Then do the same to the other side.

                          Da: warrenallgyer <allgyer@...>
                          A: softrock40@yahoogroups.com
                          Inviato: Giovedì 1 Novembre 2012 0:16
                          Oggetto: [softrock40] Re: Bad chip?

                           
                          Bill

                          I feel your pain.... been there, done that... more than once in fact.

                          A trick that will not help you now but may in the future: When removing multi-pin SMT devices I first solder all the pins together, using as little solder as possible. Then, when you apply the iron it can loosen one complete side at the same time. Carefully bending the chip up with needle nose applied to the ends will free this side. Then do the same on the other side and the chip comes up with minimal damage. Solderwick will clean up the lands and you are ready to install a replacement.

                          After many many lands lifted and chips destroyed (I am a slow-learner) this trick has saved the day many times.

                          Good luck to you.

                          Warren Allgyer - W8TOD

                          --- In softrock40@yahoogroups.com, "wfahle" <billfahle@...> wrote:
                          >
                          > Well NOW it's the chip for sure. In an attempt to remove the IC to check voltages and such, the green covering began to burn through exposing the copper traces beneath. So I got out the clippers and clipped it loose from the board, so that I could remove each lead individually. This worked, but it tore up some of the pads in the process. I intend to replace it with this chip because it is available locally (and I don't think going SMT again is going to make life any easier):



                        • Lawrence Galea
                          ps. by the way, some problems are caused by not having high enough heat and having to keep the soldering iron too long on the pcb or a soldering iron which is
                          Message 12 of 28 , Nov 1, 2012
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                            ps.
                            by the way, some problems are caused by not having high enough heat and having to keep the soldering iron too long on the pcb or a soldering iron which is not big enough to heat a big soldering pad especially when a chip or other component is already soldered or when a chip has a tab which has to be soldered to the pcb. When soldering a tab to the pcb, a 100W soldering gun will make the job much quicker and easier with less chance of damage to the pcb and the component than a soldering iron with a very fine tip as the time needed with the gun will be just a second or two while it will take much longer with a small fine-tipped iron. This is apart form the soldering being much easier and neater
                            Hope this helps.
                            Regards
                            Lawrence




                            Da: Lawrence Galea <galea_lawrence@...>
                            A: "softrock40@yahoogroups.com" <softrock40@yahoogroups.com>
                            Inviato: Giovedì 1 Novembre 2012 8:34
                            Oggetto: Re: [softrock40] Re: Bad chip?

                             
                            Another trick is to tread a thin insulated wire or a wire which does not take solder easily under the pins on one side, solder the end of the wire to a suitable solder pad near one side of the chip, then heat the pins one by one starting from the one farthest away from where you soldered the wire to the solder pad and when the solder melts pull the wire under the pin. This will push up the pin from the pcb. Do all the pins on one side and them to the other side.
                            Regards
                            Lawrence
                                                          Chip pins
                                                                 ----------------
                             Solder pad  0-------------------------------------------------------Wire
                                                                 |                      |
                                                                     Chip
                                                                 ----------------

                            Hope this explains.
                            0 is solder pad where wire is soldered
                            First heat the pin from the right hand side on the diagram and when solder melts pull the wire under the pin to the top of the page in this diagram and move towards the left pin by pin.
                            Then do the same to the other side.

                            Da: warrenallgyer <allgyer@...>
                            A: softrock40@yahoogroups.com
                            Inviato: Giovedì 1 Novembre 2012 0:16
                            Oggetto: [softrock40] Re: Bad chip?

                             
                            Bill

                            I feel your pain.... been there, done that... more than once in fact.

                            A trick that will not help you now but may in the future: When removing multi-pin SMT devices I first solder all the pins together, using as little solder as possible. Then, when you apply the iron it can loosen one complete side at the same time. Carefully bending the chip up with needle nose applied to the ends will free this side. Then do the same on the other side and the chip comes up with minimal damage. Solderwick will clean up the lands and you are ready to install a replacement.

                            After many many lands lifted and chips destroyed (I am a slow-learner) this trick has saved the day many times.

                            Good luck to you.

                            Warren Allgyer - W8TOD

                            --- In softrock40@yahoogroups.com, "wfahle" <billfahle@...> wrote:
                            >
                            > Well NOW it's the chip for sure. In an attempt to remove the IC to check voltages and such, the green covering began to burn through exposing the copper traces beneath. So I got out the clippers and clipped it loose from the board, so that I could remove each lead individually. This worked, but it tore up some of the pads in the process. I intend to replace it with this chip because it is available locally (and I don't think going SMT again is going to make life any easier):





                          • John
                            Yes thats what I do, works very well. I use fine enamelled copper wire, the type that you have to scrape the enamel off of not the type where the enamel comes
                            Message 13 of 28 , Nov 1, 2012
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                              Yes thats what I do, works very well.  I use fine enamelled copper wire, the type that you have to scrape the enamel off of not the type where the enamel comes off with heat.
                               
                              For removing the Si570 I use a heat gun.
                               
                              John G3UGY   
                               

                              Sent: Thursday, November 01, 2012 7:34 AM
                              Subject: Re: [softrock40] Re: Bad chip?

                               

                              Another trick is to tread a thin insulated wire or a wire which does not take solder easily under the pins on one side, solder the end of the wire to a suitable solder pad near one side of the chip, then heat the pins one by one starting from the one farthest away from where you soldered the wire to the solder pad and when the solder melts pull the wire under the pin. This will push up the pin from the pcb. Do all the pins on one side and them to the other side.
                              Regards
                              Lawrence
                            • wfahle
                              Good to know. In other news, the unit is no longer kerchunking when connected to USB. I mentioned elsewhere that I was able to receive a garbled SSB signal and
                              Message 14 of 28 , Nov 1, 2012
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                                Good to know. In other news, the unit is no longer kerchunking when connected to USB. I mentioned elsewhere that I was able to receive a garbled SSB signal and an intelligible CW signal with a hallway dipole after completing the receiver stage of the build, but now it no longer responds to the computer at all. So this one is bricked; I must have discharged static into it at some point, explaining the other chip failure too.

                                I am off to order another kit and a wrist strap/static mat. I hadn't been taking any particular precautions with regard to static, and having successfully built through the receiver stage I got complacent. I was building in a carpeted room with a non-grounded solder station (http://www.frys.com/product/4825200?source=googleps&gclid=CLqxhPPlrbMCFZGPPAodRz4ASQ) and touching the leads with reckless abandon, so lesson learned there. I think it was the fuzzy slippers and the tesla coil that finally did me in.

                                By the way, I don't consider this build a failure because of all I learned along the way. The next build will go much faster and be cleaner and better. I was never happy with the way I left some of the power supply capacitors floating 1/8" off the board now that I know how to avoid it, so that would have bugged me through the life of the radio. I also put a resistor in upside down (affecting only readability of the part), which admittedly is a small thing compared with a dead USB controller and a noisy radio.

                                Bill K5WL

                                --- In softrock40@yahoogroups.com, "MICHAEL TALLENT" <mwtallent@...> wrote:
                                >
                                > You really want a low noise op-amp for this application as it will determine
                                > the noise floor of your receiver. The data sheet you linked looks like
                                > nothing special, so you will not get the performance that these receivers
                                > are capable of.
                                >
                                > Mike T W6MXV
                                >
                                > ----- Original Message -----
                                > From: "wfahle" <billfahle@...>
                                > To: <softrock40@yahoogroups.com>
                                > Sent: Wednesday, October 31, 2012 12:31 PM
                                > Subject: [softrock40] Re: Bad chip?
                                >
                                >
                                > > Well NOW it's the chip for sure. In an attempt to remove the IC to check
                                > > voltages and such, the green covering began to burn through exposing the
                                > > copper traces beneath. So I got out the clippers and clipped it loose from
                                > > the board, so that I could remove each lead individually. This worked, but
                                > > it tore up some of the pads in the process. I intend to replace it with
                                > > this chip because it is available locally (and I don't think going SMT
                                > > again is going to make life any easier):
                                > > http://www.nteinc.com/specs/700to799/pdf/nte778a.pdf
                                > >
                                > > --- In softrock40@yahoogroups.com, "wfahle" <billfahle@> wrote:
                                > >>
                                > >> Ok, I pulled R16, and it still reads 5v at pin 1. R16 measures out at 10k
                                > >> as it should, but with it pulled there is very little voltage at pin 2.
                                > >> The current, since I can now measure it, across R16 is .24mA. The votage
                                > >> at pin 7 doesn't change either; it's still almost zero. The others
                                > >> besides 2 are unchanged. Pin 2 goes almost to zero vs. the 2.5 it had
                                > >> been reading. I guess R16 becomes part of a voltage divider under the
                                > >> circumstances; I don't understand circuits this complex. So I will try to
                                > >> unseat U6 and see if there is a solder bridge under it from 1 to 8 or
                                > >> something (they are across from each other).
                                >
                              • wfahle
                                See the epitaph elsewhere in this thread. I was using a 50W velleman temperature controlled soldering station, with a 3mm tip, which seems to have worked in
                                Message 15 of 28 , Nov 1, 2012
                                • 0 Attachment
                                  See the epitaph elsewhere in this thread. I was using a 50W velleman temperature controlled soldering station, with a 3mm tip, which seems to have worked in most cases except for the removal. If you look at the pictures I think you will agree it was a fine soldering job; I never spent more than a second or two with the iron to the board, except maybe when soldering ground leads for resistors and such. That copper can suck up the heat.

                                  I suspect a static hit, as I was taking few precautions and another chip bit the dust somewhere in there too (not to mention a temperature drop requiring the heater to be run).

                                  --- In softrock40@yahoogroups.com, Lawrence Galea <galea_lawrence@...> wrote:
                                  >
                                  > ps.
                                  > by the way, some problems are caused by not having high enough heat and having to keep the soldering iron too long on the pcb or a soldering iron which is not big enough to heat a big soldering pad especially when a chip or other component is already soldered or when a chip has a tab which has to be soldered to the pcb. When soldering a tab to the pcb, a 100W soldering gun will make the job much quicker and easier with less chance of damage to the pcb and the component than a soldering iron with a very fine tip as the time needed with the gun will be just a second or two while it will take much longer with a small fine-tipped iron. This is apart form the soldering being much easier and neater
                                  > Hope this helps.
                                  > Regards
                                  > Lawrence
                                  >
                                  >
                                  >
                                  >
                                  >
                                  > ________________________________
                                  > Da: Lawrence Galea <galea_lawrence@...>
                                  > A: "softrock40@yahoogroups.com" <softrock40@yahoogroups.com>
                                  > Inviato: Giovedì 1 Novembre 2012 8:34
                                  > Oggetto: Re: [softrock40] Re: Bad chip?
                                  >
                                  >
                                  >  
                                  > Another trick is to tread a thin insulated wire or a wire which does not take solder easily under the pins on one side, solder the end of the wire to a suitable solder pad near one side of the chip, then heat the pins one by one starting from the one farthest away from where you soldered the wire to the solder pad and when the solder melts pull the wire under the pin. This will push up the pin from the pcb. Do all the pins on one side and them to the other side.
                                  > Regards
                                  > Lawrence
                                  >
                                  >                               Chip pins
                                  >
                                  >                                      ----------------
                                  >  Solder pad  0-------------------------------------------------------Wire
                                  >
                                  >                                      |                      |
                                  >                                          Chip
                                  >
                                  >                                      ----------------
                                  >
                                  >
                                  > Hope this explains.
                                  >
                                  > 0 is solder pad where wire is soldered
                                  > First heat the pin from the right hand side on the diagram and when solder melts pull the wire under the pin to the top of the page in this diagram and move towards the left pin by pin.
                                  >
                                  > Then do the same to the other side.
                                  >
                                  > ________________________________
                                  > Da: warrenallgyer <allgyer@...>
                                  > A: softrock40@yahoogroups.com
                                  > Inviato: Giovedì 1 Novembre 2012 0:16
                                  > Oggetto: [softrock40] Re: Bad chip?
                                  >
                                  >
                                  >  
                                  > Bill
                                  >
                                  > I feel your pain.... been there, done that... more than once in fact.
                                  >
                                  > A trick that will not help you now but may in the future: When removing multi-pin SMT devices I first solder all the pins together, using as little solder as possible. Then, when you apply the iron it can loosen one complete side at the same time. Carefully bending the chip up with needle nose applied to the ends will free this side. Then do the same on the other side and the chip comes up with minimal damage. Solderwick will clean up the lands and you are ready to install a replacement.
                                  >
                                  > After many many lands lifted and chips destroyed (I am a slow-learner) this trick has saved the day many times.
                                  >
                                  > Good luck to you.
                                  >
                                  > Warren Allgyer - W8TOD
                                  >
                                  > --- In softrock40@yahoogroups.com, "wfahle" <billfahle@> wrote:
                                  > >
                                  > > Well NOW it's the chip for sure. In an attempt to remove the IC to check voltages and such, the green covering began to burn through exposing the copper traces beneath. So I got out the clippers and clipped it loose from the board, so that I could remove each lead individually. This worked, but it tore up some of the pads in the process. I intend to replace it with this chip because it is available locally (and I don't think going SMT again is going to make life any easier):
                                  >
                                • Sid Boyce
                                  You can consider yourself lucky if a zap killed the device rather than weakening it and causing intermittent problems may be some time way after it has been
                                  Message 16 of 28 , Nov 1, 2012
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                                    You can consider yourself lucky if a zap killed the device rather than weakening it and causing intermittent problems may be some time way after it has been working perfectly.

                                    ESD precautions are always advised.
                                    73 ... Sid.

                                    On 01/11/12 13:00, wfahle wrote:
                                     

                                    See the epitaph elsewhere in this thread. I was using a 50W velleman temperature controlled soldering station, with a 3mm tip, which seems to have worked in most cases except for the removal. If you look at the pictures I think you will agree it was a fine soldering job; I never spent more than a second or two with the iron to the board, except maybe when soldering ground leads for resistors and such. That copper can suck up the heat.

                                    I suspect a static hit, as I was taking few precautions and another chip bit the dust somewhere in there too (not to mention a temperature drop requiring the heater to be run).

                                    --- In softrock40@yahoogroups.com, Lawrence Galea <galea_lawrence@...> wrote:
                                    >
                                    > ps.
                                    > by the way, some problems are caused by not having high enough heat and having to keep the soldering iron too long on the pcb or a soldering iron which is not big enough to heat a big soldering pad especially when a chip or other component is already soldered or when a chip has a tab which has to be soldered to the pcb. When soldering a tab to the pcb, a 100W soldering gun will make the job much quicker and easier with less chance of damage to the pcb and the component than a soldering iron with a very fine tip as the time needed with the gun will be just a second or two while it will take much longer with a small fine-tipped iron. This is apart form the soldering being much easier and neater
                                    > Hope this helps.
                                    > Regards
                                    > Lawrence
                                    >
                                    >
                                    >
                                    >
                                    >
                                    > ________________________________
                                    > Da: Lawrence Galea <galea_lawrence@...>
                                    > A: "softrock40@yahoogroups.com" <softrock40@yahoogroups.com>
                                    > Inviato: Giovedì 1 Novembre 2012 8:34
                                    > Oggetto: Re: [softrock40] Re: Bad chip?
                                    >
                                    >
                                    >  
                                    > Another trick is to tread a thin insulated wire or a wire which does not take solder easily under the pins on one side, solder the end of the wire to a suitable solder pad near one side of the chip, then heat the pins one by one starting from the one farthest away from where you soldered the wire to the solder pad and when the solder melts pull the wire under the pin. This will push up the pin from the pcb. Do all the pins on one side and them to the other side.
                                    > Regards
                                    > Lawrence
                                    >
                                    >                               Chip pins
                                    >
                                    >                                      ----------------
                                    >  Solder pad  0-------------------------------------------------------Wire
                                    >
                                    >                                      |                      |
                                    >                                          Chip
                                    >
                                    >                                      ----------------
                                    >
                                    >
                                    > Hope this explains.
                                    >
                                    > 0 is solder pad where wire is soldered
                                    > First heat the pin from the right hand side on the diagram and when solder melts pull the wire under the pin to the top of the page in this diagram and move towards the left pin by pin.
                                    >
                                    > Then do the same to the other side.
                                    >
                                    > ________________________________
                                    > Da: warrenallgyer <allgyer@...>
                                    > A: softrock40@yahoogroups.com
                                    > Inviato: Giovedì 1 Novembre 2012 0:16
                                    > Oggetto: [softrock40] Re: Bad chip?
                                    >
                                    >
                                    >  
                                    > Bill
                                    >
                                    > I feel your pain.... been there, done that... more than once in fact.
                                    >
                                    > A trick that will not help you now but may in the future: When removing multi-pin SMT devices I first solder all the pins together, using as little solder as possible. Then, when you apply the iron it can loosen one complete side at the same time. Carefully bending the chip up with needle nose applied to the ends will free this side. Then do the same on the other side and the chip comes up with minimal damage. Solderwick will clean up the lands and you are ready to install a replacement.
                                    >
                                    > After many many lands lifted and chips destroyed (I am a slow-learner) this trick has saved the day many times.
                                    >
                                    > Good luck to you.
                                    >
                                    > Warren Allgyer - W8TOD
                                    >
                                    > --- In softrock40@yahoogroups.com, "wfahle" <billfahle@> wrote:
                                    > >
                                    > > Well NOW it's the chip for sure. In an attempt to remove the IC to check voltages and such, the green covering began to burn through exposing the copper traces beneath. So I got out the clippers and clipped it loose from the board, so that I could remove each lead individually. This worked, but it tore up some of the pads in the process. I intend to replace it with this chip because it is available locally (and I don't think going SMT again is going to make life any easier):
                                    >



                                    -- 
                                    Sid Boyce ... Hamradio License G3VBV, Licensed Private Pilot
                                    Emeritus IBM/Amdahl Mainframes and Sun/Fujitsu Servers Tech Support
                                    Senior Staff Specialist, Cricket Coach
                                    Microsoft Windows Free Zone - Linux used for all Computing Tasks
                                    
                                  • wfahle
                                    It s embarrassing to admit this but here goes: Problem: unit doesn t kerchunk when connecting to USB Solution: pick up the earphones off the desk. ... Mind
                                    Message 17 of 28 , Nov 1, 2012
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                                      It's embarrassing to admit this but here goes:
                                      Problem: unit doesn't kerchunk when connecting to USB
                                      Solution: pick up the earphones off the desk.
                                      :/

                                      Mind you, the voltage was still bad on that one chip. So I do have work to do if I want a transmitter. Received a good signal again tonight.

                                      --- In softrock40@yahoogroups.com, Sid Boyce <sboyce@...> wrote:
                                      >
                                      > You can consider yourself lucky if a zap killed the device rather than
                                      > weakening it and causing intermittent problems may be some time way
                                      > after it has been working perfectly.
                                      >
                                      > ESD precautions are always advised.
                                      > 73 ... Sid.
                                      >
                                      > On 01/11/12 13:00, wfahle wrote:
                                      > >
                                      > > See the epitaph elsewhere in this thread. I was using a 50W velleman
                                      > > temperature controlled soldering station, with a 3mm tip, which seems
                                      > > to have worked in most cases except for the removal. If you look at
                                      > > the pictures I think you will agree it was a fine soldering job; I
                                      > > never spent more than a second or two with the iron to the board,
                                      > > except maybe when soldering ground leads for resistors and such. That
                                      > > copper can suck up the heat.
                                      > >
                                      > > I suspect a static hit, as I was taking few precautions and another
                                      > > chip bit the dust somewhere in there too (not to mention a temperature
                                      > > drop requiring the heater to be run).
                                      > >
                                      > > --- In softrock40@yahoogroups.com
                                      > > <mailto:softrock40%40yahoogroups.com>, Lawrence Galea
                                      > > <galea_lawrence@> wrote:
                                      > > >
                                      > > > ps.
                                      > > > by the way, some problems are caused by not having high enough heat
                                      > > and having to keep the soldering iron too long on the pcb or a
                                      > > soldering iron which is not big enough to heat a big soldering pad
                                      > > especially when a chip or other component is already soldered or when
                                      > > a chip has a tab which has to be soldered to the pcb. When soldering a
                                      > > tab to the pcb, a 100W soldering gun will make the job much quicker
                                      > > and easier with less chance of damage to the pcb and the component
                                      > > than a soldering iron with a very fine tip as the time needed with the
                                      > > gun will be just a second or two while it will take much longer with a
                                      > > small fine-tipped iron. This is apart form the soldering being much
                                      > > easier and neater
                                      > > > Hope this helps.
                                      > > > Regards
                                      > > > Lawrence
                                      > > >
                                      > > >
                                      > > >
                                      > > >
                                      > > >
                                      > > > ________________________________
                                      > > > Da: Lawrence Galea <galea_lawrence@>
                                      > > > A: "softrock40@yahoogroups.com
                                      > > <mailto:softrock40%40yahoogroups.com>" <softrock40@yahoogroups.com
                                      > > <mailto:softrock40%40yahoogroups.com>>
                                      > > > Inviato: Giovedì 1 Novembre 2012 8:34
                                      > > > Oggetto: Re: [softrock40] Re: Bad chip?
                                      > > >
                                      > > >
                                      > > > Â
                                      > > > Another trick is to tread a thin insulated wire or a wire which does
                                      > > not take solder easily under the pins on one side, solder the end of
                                      > > the wire to a suitable solder pad near one side of the chip, then heat
                                      > > the pins one by one starting from the one farthest away from where you
                                      > > soldered the wire to the solder pad and when the solder melts pull the
                                      > > wire under the pin. This will push up the pin from the pcb. Do all the
                                      > > pins on one side and them to the other side.
                                      > > > Regards
                                      > > > Lawrence
                                      > > >
                                      > > > Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Chip pins
                                      > > >
                                      > > > Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
                                      > > ----------------
                                      > > > Â Solder padÂ
                                      > > 0-------------------------------------------------------Wire
                                      > > >
                                      > > > Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
                                      > > |Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â |
                                      > > >
                                      > > Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
                                      > > Chip
                                      > > >
                                      > > >
                                      > > Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â ----------------
                                      > > >
                                      > > >
                                      > > > Hope this explains.
                                      > > >
                                      > > > 0 is solder pad where wire is soldered
                                      > > > First heat the pin from the right hand side on the diagram and when
                                      > > solder melts pull the wire under the pin to the top of the page in
                                      > > this diagram and move towards the left pin by pin.
                                      > > >
                                      > > > Then do the same to the other side.
                                      > > >
                                      > > > ________________________________
                                      > > > Da: warrenallgyer <allgyer@>
                                      > > > A: softrock40@yahoogroups.com <mailto:softrock40%40yahoogroups.com>
                                      > > > Inviato: Giovedì 1 Novembre 2012 0:16
                                      > > > Oggetto: [softrock40] Re: Bad chip?
                                      > > >
                                      > > >
                                      > > > Â
                                      > > > Bill
                                      > > >
                                      > > > I feel your pain.... been there, done that... more than once in fact.
                                      > > >
                                      > > > A trick that will not help you now but may in the future: When
                                      > > removing multi-pin SMT devices I first solder all the pins together,
                                      > > using as little solder as possible. Then, when you apply the iron it
                                      > > can loosen one complete side at the same time. Carefully bending the
                                      > > chip up with needle nose applied to the ends will free this side. Then
                                      > > do the same on the other side and the chip comes up with minimal
                                      > > damage. Solderwick will clean up the lands and you are ready to
                                      > > install a replacement.
                                      > > >
                                      > > > After many many lands lifted and chips destroyed (I am a
                                      > > slow-learner) this trick has saved the day many times.
                                      > > >
                                      > > > Good luck to you.
                                      > > >
                                      > > > Warren Allgyer - W8TOD
                                      > > >
                                      > > > --- In softrock40@yahoogroups.com
                                      > > <mailto:softrock40%40yahoogroups.com>, "wfahle" <billfahle@> wrote:
                                      > > > >
                                      > > > > Well NOW it's the chip for sure. In an attempt to remove the IC to
                                      > > check voltages and such, the green covering began to burn through
                                      > > exposing the copper traces beneath. So I got out the clippers and
                                      > > clipped it loose from the board, so that I could remove each lead
                                      > > individually. This worked, but it tore up some of the pads in the
                                      > > process. I intend to replace it with this chip because it is available
                                      > > locally (and I don't think going SMT again is going to make life any
                                      > > easier):
                                      > > >
                                      > >
                                      > >
                                      >
                                      >
                                      > --
                                      > Sid Boyce ... Hamradio License G3VBV, Licensed Private Pilot
                                      > Emeritus IBM/Amdahl Mainframes and Sun/Fujitsu Servers Tech Support
                                      > Senior Staff Specialist, Cricket Coach
                                      > Microsoft Windows Free Zone - Linux used for all Computing Tasks
                                      >
                                    • Sid Boyce
                                      Things happen now, in the past and will in the future. We all go there - turn the speaker volume down to take a phone call and much later wonder if the SDR app
                                      Message 18 of 28 , Nov 2, 2012
                                      • 0 Attachment
                                        Things happen now, in the past and will in the future.
                                        We all go there - turn the speaker volume down to take a phone call and much later wonder if the SDR app has lost sound - been there, done that.
                                        73 ... Sid.

                                        On 02/11/12 02:32, wfahle wrote:
                                         

                                        It's embarrassing to admit this but here goes:
                                        Problem: unit doesn't kerchunk when connecting to USB
                                        Solution: pick up the earphones off the desk.
                                        :/

                                        Mind you, the voltage was still bad on that one chip. So I do have work to do if I want a transmitter. Received a good signal again tonight.

                                        --- In softrock40@yahoogroups.com, Sid Boyce <sboyce@...> wrote:
                                        >
                                        > You can consider yourself lucky if a zap killed the device rather than
                                        > weakening it and causing intermittent problems may be some time way
                                        > after it has been working perfectly.
                                        >
                                        > ESD precautions are always advised.
                                        > 73 ... Sid.
                                        >
                                        > On 01/11/12 13:00, wfahle wrote:
                                        > >
                                        > > See the epitaph elsewhere in this thread. I was using a 50W velleman
                                        > > temperature controlled soldering station, with a 3mm tip, which seems
                                        > > to have worked in most cases except for the removal. If you look at
                                        > > the pictures I think you will agree it was a fine soldering job; I
                                        > > never spent more than a second or two with the iron to the board,
                                        > > except maybe when soldering ground leads for resistors and such. That
                                        > > copper can suck up the heat.
                                        > >
                                        > > I suspect a static hit, as I was taking few precautions and another
                                        > > chip bit the dust somewhere in there too (not to mention a temperature
                                        > > drop requiring the heater to be run).
                                        > >
                                        > > --- In softrock40@yahoogroups.com
                                        > > <mailto:softrock40%40yahoogroups.com>, Lawrence Galea
                                        > > <galea_lawrence@> wrote:
                                        > > >
                                        > > > ps.
                                        > > > by the way, some problems are caused by not having high enough heat
                                        > > and having to keep the soldering iron too long on the pcb or a
                                        > > soldering iron which is not big enough to heat a big soldering pad
                                        > > especially when a chip or other component is already soldered or when
                                        > > a chip has a tab which has to be soldered to the pcb. When soldering a
                                        > > tab to the pcb, a 100W soldering gun will make the job much quicker
                                        > > and easier with less chance of damage to the pcb and the component
                                        > > than a soldering iron with a very fine tip as the time needed with the
                                        > > gun will be just a second or two while it will take much longer with a
                                        > > small fine-tipped iron. This is apart form the soldering being much
                                        > > easier and neater
                                        > > > Hope this helps.
                                        > > > Regards
                                        > > > Lawrence
                                        > > >
                                        > > >
                                        > > >
                                        > > >
                                        > > >
                                        > > > ________________________________
                                        > > > Da: Lawrence Galea <galea_lawrence@>
                                        > > > A: "softrock40@yahoogroups.com
                                        > > <mailto:softrock40%40yahoogroups.com>" <softrock40@yahoogroups.com
                                        > > <mailto:softrock40%40yahoogroups.com>>
                                        > > > Inviato: Giovedì 1 Novembre 2012 8:34
                                        > > > Oggetto: Re: [softrock40] Re: Bad chip?
                                        > > >
                                        > > >
                                        > > > Â
                                        > > > Another trick is to tread a thin insulated wire or a wire which does
                                        > > not take solder easily under the pins on one side, solder the end of
                                        > > the wire to a suitable solder pad near one side of the chip, then heat
                                        > > the pins one by one starting from the one farthest away from where you
                                        > > soldered the wire to the solder pad and when the solder melts pull the
                                        > > wire under the pin. This will push up the pin from the pcb. Do all the
                                        > > pins on one side and them to the other side.
                                        > > > Regards
                                        > > > Lawrence
                                        > > >
                                        > > > Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Chip pins
                                        > > >
                                        > > > Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
                                        > > ----------------
                                        > > > Â Solder padÂ
                                        > > 0-------------------------------------------------------Wire
                                        > > >
                                        > > > Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
                                        > > |Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â |
                                        > > >
                                        > > Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
                                        > > Chip
                                        > > >
                                        > > >
                                        > > Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â ----------------
                                        > > >
                                        > > >
                                        > > > Hope this explains.
                                        > > >
                                        > > > 0 is solder pad where wire is soldered
                                        > > > First heat the pin from the right hand side on the diagram and when
                                        > > solder melts pull the wire under the pin to the top of the page in
                                        > > this diagram and move towards the left pin by pin.
                                        > > >
                                        > > > Then do the same to the other side.
                                        > > >
                                        > > > ________________________________
                                        > > > Da: warrenallgyer <allgyer@>
                                        > > > A: softrock40@yahoogroups.com <mailto:softrock40%40yahoogroups.com>
                                        > > > Inviato: Giovedì 1 Novembre 2012 0:16
                                        > > > Oggetto: [softrock40] Re: Bad chip?
                                        > > >
                                        > > >
                                        > > > Â
                                        > > > Bill
                                        > > >
                                        > > > I feel your pain.... been there, done that... more than once in fact.
                                        > > >
                                        > > > A trick that will not help you now but may in the future: When
                                        > > removing multi-pin SMT devices I first solder all the pins together,
                                        > > using as little solder as possible. Then, when you apply the iron it
                                        > > can loosen one complete side at the same time. Carefully bending the
                                        > > chip up with needle nose applied to the ends will free this side. Then
                                        > > do the same on the other side and the chip comes up with minimal
                                        > > damage. Solderwick will clean up the lands and you are ready to
                                        > > install a replacement.
                                        > > >
                                        > > > After many many lands lifted and chips destroyed (I am a
                                        > > slow-learner) this trick has saved the day many times.
                                        > > >
                                        > > > Good luck to you.
                                        > > >
                                        > > > Warren Allgyer - W8TOD
                                        > > >
                                        > > > --- In softrock40@yahoogroups.com
                                        > > <mailto:softrock40%40yahoogroups.com>, "wfahle" <billfahle@> wrote:
                                        > > > >
                                        > > > > Well NOW it's the chip for sure. In an attempt to remove the IC to
                                        > > check voltages and such, the green covering began to burn through
                                        > > exposing the copper traces beneath. So I got out the clippers and
                                        > > clipped it loose from the board, so that I could remove each lead
                                        > > individually. This worked, but it tore up some of the pads in the
                                        > > process. I intend to replace it with this chip because it is available
                                        > > locally (and I don't think going SMT again is going to make life any
                                        > > easier):
                                        > > >
                                        > >
                                        > >
                                        >
                                        >
                                        > --
                                        > Sid Boyce ... Hamradio License G3VBV, Licensed Private Pilot
                                        > Emeritus IBM/Amdahl Mainframes and Sun/Fujitsu Servers Tech Support
                                        > Senior Staff Specialist, Cricket Coach
                                        > Microsoft Windows Free Zone - Linux used for all Computing Tasks
                                        >



                                        -- 
                                        Sid Boyce ... Hamradio License G3VBV, Licensed Private Pilot
                                        Emeritus IBM/Amdahl Mainframes and Sun/Fujitsu Servers Tech Support
                                        Senior Staff Specialist, Cricket Coach
                                        Microsoft Windows Free Zone - Linux used for all Computing Tasks
                                        
                                      • John Rabson
                                        ... When I was running the e-mail system for a major organisation, I received an annoyed phone call from the Director one Monday morning, complaining that his
                                        Message 19 of 28 , Nov 2, 2012
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                                          On 2 Nov 2012, at 12:39CET, Sid Boyce wrote:

                                           

                                          Things happen now, in the past and will in the future.
                                          We all go there - turn the speaker volume down to take a phone call and much later wonder if the SDR app has lost sound - been there, done that.
                                          73 ... Sid.

                                          When I was running the e-mail system for a major organisation, I received an annoyed phone call from the Director one Monday morning, complaining that his e-mail system did not work.

                                          I sent my most diplomatic technician to find out what had happened. He reported back a few minutes later -  the client had forgotten to switch his monitor on (in those days monitors tended to have separate power feeds and were always switched off at the weekend).

                                          John F5VLF


                                        • wfahle
                                          Well I m a mere Ph.D. in computer science with 20 years in the industry, so yes, I ve done this sort of thing dozens of times! PEBKAC
                                          Message 20 of 28 , Nov 2, 2012
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                                            Well I'm a mere Ph.D. in computer science with 20 years in the industry, so yes, I've done this sort of thing dozens of times! PEBKAC

                                            --- In softrock40@yahoogroups.com, John Rabson <john.rabson@...> wrote:
                                            >
                                            > On 2 Nov 2012, at 12:39CET, Sid Boyce wrote:
                                            >
                                            > >
                                            > > Things happen now, in the past and will in the future.
                                            > > We all go there - turn the speaker volume down to take a phone call and much later wonder if the SDR app has lost sound - been there, done that.
                                            > > 73 ... Sid.
                                            >
                                            > When I was running the e-mail system for a major organisation, I received an annoyed phone call from the Director one Monday morning, complaining that his e-mail system did not work.
                                            >
                                            > I sent my most diplomatic technician to find out what had happened. He reported back a few minutes later - the client had forgotten to switch his monitor on (in those days monitors tended to have separate power feeds and were always switched off at the weekend).
                                            >
                                            > John F5VLF
                                            > >
                                            >
                                          • Anthony Casorso
                                            PHd? Well, that explains it! ;) TonyBS EE (But master of BS)To: softrock40@yahoogroups.com From: billfahle@gmail.com Date: Fri, 2 Nov 2012 13:23:45 +0000
                                            Message 21 of 28 , Nov 2, 2012
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                                               PHd?  Well, that explains it!   ;)
                                               
                                              Tony
                                              BS EE (But master of BS)

                                              To: softrock40@yahoogroups.com
                                              From: billfahle@...
                                              Date: Fri, 2 Nov 2012 13:23:45 +0000
                                              Subject: [softrock40] Re: Bad chip?

                                               
                                              Well I'm a mere Ph.D. in computer science with 20 years in the industry, so yes, I've done this sort of thing dozens of times! PEBKAC

                                              --- In softrock40@yahoogroups.com, John Rabson <john.rabson@...> wrote:
                                              >
                                              > On 2 Nov 2012, at 12:39CET, Sid Boyce wrote:
                                              >
                                              > >
                                              > > Things happen now, in the past and will in the future.
                                              > > We all go there - turn the speaker volume down to take a phone call and much later wonder if the SDR app has lost sound - been there, done that.
                                              > > 73 ... Sid.
                                              >
                                              > When I was running the e-mail system for a major organisation, I received an annoyed phone call from the Director one Monday morning, complaining that his e-mail system did not work.
                                              >
                                              > I sent my most diplomatic technician to find out what had happened. He reported back a few minutes later - the client had forgotten to switch his monitor on (in those days monitors tended to have separate power feeds and were always switched off at the weekend).
                                              >
                                              > John F5VLF
                                              > >
                                              >


                                            • John Greusel
                                              I just had one recently- I was certain I had blown the BS170s with an inadvertent key down for 10 minutes and replaced them. Turned out it was a short in the
                                              Message 22 of 28 , Nov 2, 2012
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                                                I just had one recently- I was certain I had blown the BS170s with an inadvertent key down for 10 minutes and replaced them.
                                                Turned out it was a short in the microphone. The noise was horrendous.

                                                John
                                                KC9OJV

                                                 



                                                From: Sid Boyce <sboyce@...>
                                                To: softrock40@yahoogroups.com
                                                Sent: Friday, November 2, 2012 6:39 AM
                                                Subject: Re: [softrock40] Re: Bad chip?

                                                 
                                                Things happen now, in the past and will in the future.
                                                We all go there - turn the speaker volume down to take a phone call and much later wonder if the SDR app has lost sound - been there, done that.
                                                73 ... Sid.

                                                On 02/11/12 02:32, wfahle wrote:
                                                 
                                                It's embarrassing to admit this but here goes:
                                                Problem: unit doesn't kerchunk when connecting to USB
                                                Solution: pick up the earphones off the desk.
                                                :/

                                                Mind you, the voltage was still bad on that one chip. So I do have work to do if I want a transmitter. Received a good signal again tonight.

                                                --- In softrock40@yahoogroups.com, Sid Boyce <sboyce@...> wrote:
                                                >
                                                > You can consider yourself lucky if a zap killed the device rather than
                                                > weakening it and causing intermittent problems may be some time way
                                                > after it has been working perfectly.
                                                >
                                                > ESD precautions are always advised.
                                                > 73 ... Sid.
                                                >
                                                > On 01/11/12 13:00, wfahle wrote:
                                                > >
                                                > > See the epitaph elsewhere in this thread. I was using a 50W velleman
                                                > > temperature controlled soldering station, with a 3mm tip, which seems
                                                > > to have worked in most cases except for the removal. If you look at
                                                > > the pictures I think you will agree it was a fine soldering job; I
                                                > > never spent more than a second or two with the iron to the board,
                                                > > except maybe when soldering ground leads for resistors and such. That
                                                > > copper can suck up the heat.
                                                > >
                                                > > I suspect a static hit, as I was taking few precautions and another
                                                > > chip bit the dust somewhere in there too (not to mention a temperature
                                                > > drop requiring the heater to be run).
                                                > >
                                                > > --- In softrock40@yahoogroups.com
                                                > > <mailto:softrock40%40yahoogroups.com>, Lawrence Galea
                                                > > <galea_lawrence@> wrote:
                                                > > >
                                                > > > ps.
                                                > > > by the way, some problems are caused by not having high enough heat
                                                > > and having to keep the soldering iron too long on the pcb or a
                                                > > soldering iron which is not big enough to heat a big soldering pad
                                                > > especially when a chip or other component is already soldered or when
                                                > > a chip has a tab which has to be soldered to the pcb. When soldering a
                                                > > tab to the pcb, a 100W soldering gun will make the job much quicker
                                                > > and easier with less chance of damage to the pcb and the component
                                                > > than a soldering iron with a very fine tip as the time needed with the
                                                > > gun will be just a second or two while it will take much longer with a
                                                > > small fine-tipped iron. This is apart form the soldering being much
                                                > > easier and neater
                                                > > > Hope this helps.
                                                > > > Regards
                                                > > > Lawrence
                                                > > >
                                                > > >
                                                > > >
                                                > > >
                                                > > >
                                                > > > ________________________________
                                                > > > Da: Lawrence Galea <galea_lawrence@>
                                                > > > A: "softrock40@yahoogroups.com
                                                > > <mailto:softrock40%40yahoogroups.com>" <softrock40@yahoogroups.com
                                                > > <mailto:softrock40%40yahoogroups.com>>
                                                > > > Inviato: Giovedì 1 Novembre 2012 8:34
                                                > > > Oggetto: Re: [softrock40] Re: Bad chip?
                                                > > >
                                                > > >
                                                > > > Â
                                                > > > Another trick is to tread a thin insulated wire or a wire which does
                                                > > not take solder easily under the pins on one side, solder the end of
                                                > > the wire to a suitable solder pad near one side of the chip, then heat
                                                > > the pins one by one starting from the one farthest away from where you
                                                > > soldered the wire to the solder pad and when the solder melts pull the
                                                > > wire under the pin. This will push up the pin from the pcb. Do all the
                                                > > pins on one side and them to the other side.
                                                > > > Regards
                                                > > > Lawrence
                                                > > >
                                                > > > Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Chip pins
                                                > > >
                                                > > > Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
                                                > > ----------------
                                                > > > Â Solder padÂ
                                                > > 0-------------------------------------------------------Wire
                                                > > >
                                                > > > Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
                                                > > |Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â |
                                                > > >
                                                > > Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â
                                                > > Chip
                                                > > >
                                                > > >
                                                > > Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â ----------------
                                                > > >
                                                > > >
                                                > > > Hope this explains.
                                                > > >
                                                > > > 0 is solder pad where wire is soldered
                                                > > > First heat the pin from the right hand side on the diagram and when
                                                > > solder melts pull the wire under the pin to the top of the page in
                                                > > this diagram and move towards the left pin by pin.
                                                > > >
                                                > > > Then do the same to the other side.
                                                > > >
                                                > > > ________________________________
                                                > > > Da: warrenallgyer <allgyer@>
                                                > > > A: softrock40@yahoogroups.com <mailto:softrock40%40yahoogroups.com>
                                                > > > Inviato: Giovedì 1 Novembre 2012 0:16
                                                > > > Oggetto: [softrock40] Re: Bad chip?
                                                > > >
                                                > > >
                                                > > > Â
                                                > > > Bill
                                                > > >
                                                > > > I feel your pain.... been there, done that... more than once in fact.
                                                > > >
                                                > > > A trick that will not help you now but may in the future: When
                                                > > removing multi-pin SMT devices I first solder all the pins together,
                                                > > using as little solder as possible. Then, when you apply the iron it
                                                > > can loosen one complete side at the same time. Carefully bending the
                                                > > chip up with needle nose applied to the ends will free this side. Then
                                                > > do the same on the other side and the chip comes up with minimal
                                                > > damage. Solderwick will clean up the lands and you are ready to
                                                > > install a replacement.
                                                > > >
                                                > > > After many many lands lifted and chips destroyed (I am a
                                                > > slow-learner) this trick has saved the day many times.
                                                > > >
                                                > > > Good luck to you.
                                                > > >
                                                > > > Warren Allgyer - W8TOD
                                                > > >
                                                > > > --- In softrock40@yahoogroups.com
                                                > > <mailto:softrock40%40yahoogroups.com>, "wfahle" <billfahle@> wrote:
                                                > > > >
                                                > > > > Well NOW it's the chip for sure. In an attempt to remove the IC to
                                                > > check voltages and such, the green covering began to burn through
                                                > > exposing the copper traces beneath. So I got out the clippers and
                                                > > clipped it loose from the board, so that I could remove each lead
                                                > > individually. This worked, but it tore up some of the pads in the
                                                > > process. I intend to replace it with this chip because it is available
                                                > > locally (and I don't think going SMT again is going to make life any
                                                > > easier):
                                                > > >
                                                > >
                                                > >
                                                >
                                                >
                                                > --
                                                > Sid Boyce ... Hamradio License G3VBV, Licensed Private Pilot
                                                > Emeritus IBM/Amdahl Mainframes and Sun/Fujitsu Servers Tech Support
                                                > Senior Staff Specialist, Cricket Coach
                                                > Microsoft Windows Free Zone - Linux used for all Computing Tasks
                                                >



                                                -- 
                                                Sid Boyce ... Hamradio License G3VBV, Licensed Private Pilot
                                                Emeritus IBM/Amdahl Mainframes and Sun/Fujitsu Servers Tech Support
                                                Senior Staff Specialist, Cricket Coach
                                                Microsoft Windows Free Zone - Linux used for all Computing Tasks
                                                


                                              • wfahle
                                                Ok, I ve recovered from the brain fart, and am back on track now. This OP-Amp (dual) is in the transmitter, as U6. Do you think noise will cause a problem? I
                                                Message 23 of 28 , Nov 2, 2012
                                                • 0 Attachment
                                                  Ok, I've recovered from the brain fart, and am back on track now. This OP-Amp (dual) is in the transmitter, as U6. Do you think noise will cause a problem? I think I will try it anyway this weekend, because I am installing it dead-bug style with individual wires to each lead, so it will be easily replaced. This will allow me to finish the transmitter and see what I get signal-report wise.

                                                  --- In softrock40@yahoogroups.com, "MICHAEL TALLENT" <mwtallent@...> wrote:
                                                  >
                                                  > You really want a low noise op-amp for this application as it will determine
                                                  > the noise floor of your receiver. The data sheet you linked looks like
                                                  > nothing special, so you will not get the performance that these receivers
                                                  > are capable of.
                                                  >
                                                  > Mike T W6MXV
                                                  >
                                                  > ----- Original Message -----
                                                  > From: "wfahle" <billfahle@...>
                                                  > To: <softrock40@yahoogroups.com>
                                                  > Sent: Wednesday, October 31, 2012 12:31 PM
                                                  > Subject: [softrock40] Re: Bad chip?
                                                  >
                                                  >
                                                  > > Well NOW it's the chip for sure. In an attempt to remove the IC to check
                                                  > > voltages and such, the green covering began to burn through exposing the
                                                  > > copper traces beneath. So I got out the clippers and clipped it loose from
                                                  > > the board, so that I could remove each lead individually. This worked, but
                                                  > > it tore up some of the pads in the process. I intend to replace it with
                                                  > > this chip because it is available locally (and I don't think going SMT
                                                  > > again is going to make life any easier):
                                                  > > http://www.nteinc.com/specs/700to799/pdf/nte778a.pdf
                                                  > >
                                                  > > --- In softrock40@yahoogroups.com, "wfahle" <billfahle@> wrote:
                                                  > >>
                                                  > >> Ok, I pulled R16, and it still reads 5v at pin 1. R16 measures out at 10k
                                                  > >> as it should, but with it pulled there is very little voltage at pin 2.
                                                  > >> The current, since I can now measure it, across R16 is .24mA. The votage
                                                  > >> at pin 7 doesn't change either; it's still almost zero. The others
                                                  > >> besides 2 are unchanged. Pin 2 goes almost to zero vs. the 2.5 it had
                                                  > >> been reading. I guess R16 becomes part of a voltage divider under the
                                                  > >> circumstances; I don't understand circuits this complex. So I will try to
                                                  > >> unseat U6 and see if there is a solder bridge under it from 1 to 8 or
                                                  > >> something (they are across from each other).
                                                  >
                                                • MICHAEL TALLENT
                                                  Noise probably will not matter for the transmitting side, the output level may not be as good as amps designed for low voltage operation, but try it and see.
                                                  Message 24 of 28 , Nov 2, 2012
                                                  • 0 Attachment
                                                    Noise probably will not matter for the transmitting side, the output level
                                                    may not be as good as amps designed for low voltage operation, but try it
                                                    and see.

                                                    Mike T

                                                    ----- Original Message -----
                                                    From: "wfahle" <billfahle@...>
                                                    To: <softrock40@yahoogroups.com>
                                                    Sent: Friday, November 02, 2012 12:46 PM
                                                    Subject: [softrock40] Re: Bad chip?


                                                    > Ok, I've recovered from the brain fart, and am back on track now. This
                                                    > OP-Amp (dual) is in the transmitter, as U6. Do you think noise will cause
                                                    > a problem? I think I will try it anyway this weekend, because I am
                                                    > installing it dead-bug style with individual wires to each lead, so it
                                                    > will be easily replaced. This will allow me to finish the transmitter and
                                                    > see what I get signal-report wise.
                                                    >
                                                    > --- In softrock40@yahoogroups.com, "MICHAEL TALLENT" <mwtallent@...>
                                                    > wrote:
                                                    >>
                                                    >> You really want a low noise op-amp for this application as it will
                                                    >> determine
                                                    >> the noise floor of your receiver. The data sheet you linked looks like
                                                    >> nothing special, so you will not get the performance that these receivers
                                                    >> are capable of.
                                                    >>
                                                    >> Mike T W6MXV
                                                    >>
                                                    >> ----- Original Message -----
                                                    >> From: "wfahle" <billfahle@...>
                                                    >> To: <softrock40@yahoogroups.com>
                                                    >> Sent: Wednesday, October 31, 2012 12:31 PM
                                                    >> Subject: [softrock40] Re: Bad chip?
                                                    >>
                                                    >>
                                                    >> > Well NOW it's the chip for sure. In an attempt to remove the IC to
                                                    >> > check
                                                    >> > voltages and such, the green covering began to burn through exposing
                                                    >> > the
                                                    >> > copper traces beneath. So I got out the clippers and clipped it loose
                                                    >> > from
                                                    >> > the board, so that I could remove each lead individually. This worked,
                                                    >> > but
                                                    >> > it tore up some of the pads in the process. I intend to replace it with
                                                    >> > this chip because it is available locally (and I don't think going SMT
                                                    >> > again is going to make life any easier):
                                                    >> > http://www.nteinc.com/specs/700to799/pdf/nte778a.pdf
                                                    >> >
                                                    >> > --- In softrock40@yahoogroups.com, "wfahle" <billfahle@> wrote:
                                                    >> >>
                                                    >> >> Ok, I pulled R16, and it still reads 5v at pin 1. R16 measures out at
                                                    >> >> 10k
                                                    >> >> as it should, but with it pulled there is very little voltage at pin
                                                    >> >> 2.
                                                    >> >> The current, since I can now measure it, across R16 is .24mA. The
                                                    >> >> votage
                                                    >> >> at pin 7 doesn't change either; it's still almost zero. The others
                                                    >> >> besides 2 are unchanged. Pin 2 goes almost to zero vs. the 2.5 it had
                                                    >> >> been reading. I guess R16 becomes part of a voltage divider under the
                                                    >> >> circumstances; I don't understand circuits this complex. So I will try
                                                    >> >> to
                                                    >> >> unseat U6 and see if there is a solder bridge under it from 1 to 8 or
                                                    >> >> something (they are across from each other).
                                                    >>
                                                  • wfahle
                                                    It indicates 5v on pin 1, Just like the other one in that respect. With power off, I m currently reading 20.9 Kohms between pin 1 and pin 8, which when
                                                    Message 25 of 28 , Nov 3, 2012
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                                                      It indicates 5v on pin 1, Just like the other one in that respect. With power off, I'm currently reading 20.9 Kohms between pin 1 and pin 8, which when reviewing the schematic doesn't seem right. In fact the other dual op-amp which seems wired similarly is an open circuit between those pins, giving me more confidence that this is the problem. I'm reading 11Kohms between 8 and 2 on U6, which is probably where the 20.9 is coming from adding R16 (which spans 1 and 2). Any ideas anyone? Clearly there is a short somewhere, and not a bad chip after all.

                                                      --- In softrock40@yahoogroups.com, "MICHAEL TALLENT" <mwtallent@...> wrote:
                                                      >
                                                      > Noise probably will not matter for the transmitting side, the output level
                                                      > may not be as good as amps designed for low voltage operation, but try it
                                                      > and see.
                                                      >
                                                      > Mike T
                                                      >
                                                      > ----- Original Message -----
                                                      > From: "wfahle" <billfahle@...>
                                                      > To: <softrock40@yahoogroups.com>
                                                      > Sent: Friday, November 02, 2012 12:46 PM
                                                      > Subject: [softrock40] Re: Bad chip?
                                                      >
                                                      >
                                                      > > Ok, I've recovered from the brain fart, and am back on track now. This
                                                      > > OP-Amp (dual) is in the transmitter, as U6. Do you think noise will cause
                                                      > > a problem? I think I will try it anyway this weekend, because I am
                                                      > > installing it dead-bug style with individual wires to each lead, so it
                                                      > > will be easily replaced. This will allow me to finish the transmitter and
                                                      > > see what I get signal-report wise.
                                                      > >
                                                      > > --- In softrock40@yahoogroups.com, "MICHAEL TALLENT" <mwtallent@>
                                                      > > wrote:
                                                      > >>
                                                      > >> You really want a low noise op-amp for this application as it will
                                                      > >> determine
                                                      > >> the noise floor of your receiver. The data sheet you linked looks like
                                                      > >> nothing special, so you will not get the performance that these receivers
                                                      > >> are capable of.
                                                      > >>
                                                      > >> Mike T W6MXV
                                                      > >>
                                                      > >> ----- Original Message -----
                                                      > >> From: "wfahle" <billfahle@>
                                                      > >> To: <softrock40@yahoogroups.com>
                                                      > >> Sent: Wednesday, October 31, 2012 12:31 PM
                                                      > >> Subject: [softrock40] Re: Bad chip?
                                                      > >>
                                                      > >>
                                                      > >> > Well NOW it's the chip for sure. In an attempt to remove the IC to
                                                      > >> > check
                                                      > >> > voltages and such, the green covering began to burn through exposing
                                                      > >> > the
                                                      > >> > copper traces beneath. So I got out the clippers and clipped it loose
                                                      > >> > from
                                                      > >> > the board, so that I could remove each lead individually. This worked,
                                                      > >> > but
                                                      > >> > it tore up some of the pads in the process. I intend to replace it with
                                                      > >> > this chip because it is available locally (and I don't think going SMT
                                                      > >> > again is going to make life any easier):
                                                      > >> > http://www.nteinc.com/specs/700to799/pdf/nte778a.pdf
                                                      > >> >
                                                      > >> > --- In softrock40@yahoogroups.com, "wfahle" <billfahle@> wrote:
                                                      > >> >>
                                                      > >> >> Ok, I pulled R16, and it still reads 5v at pin 1. R16 measures out at
                                                      > >> >> 10k
                                                      > >> >> as it should, but with it pulled there is very little voltage at pin
                                                      > >> >> 2.
                                                      > >> >> The current, since I can now measure it, across R16 is .24mA. The
                                                      > >> >> votage
                                                      > >> >> at pin 7 doesn't change either; it's still almost zero. The others
                                                      > >> >> besides 2 are unchanged. Pin 2 goes almost to zero vs. the 2.5 it had
                                                      > >> >> been reading. I guess R16 becomes part of a voltage divider under the
                                                      > >> >> circumstances; I don't understand circuits this complex. So I will try
                                                      > >> >> to
                                                      > >> >> unseat U6 and see if there is a solder bridge under it from 1 to 8 or
                                                      > >> >> something (they are across from each other).
                                                      > >>
                                                      >
                                                    • Alan
                                                      ... Subject: [softrock40] Re: Bad chip? Not that one, in any case. ... I do not remember you giving the voltages you see on this chip. 73 Alan G4ZFQ
                                                      Message 26 of 28 , Nov 3, 2012
                                                      • 0 Attachment
                                                        ----- Original Message -----
                                                        Subject: [softrock40] Re: Bad chip? Not that one, in any case.


                                                        > It indicates 5v on pin 1, Just like the other one in that respect. With power off, I'm currently reading 20.9 Kohms between pin 1
                                                        > and pin 8, which when reviewing the schematic doesn't seem right. In fact the other dual op-amp which seems wired similarly is an
                                                        > open circuit between those pins, giving me more confidence that this is the problem. I'm reading 11Kohms between 8 and 2 on U6,
                                                        > which is probably where the 20.9 is coming from adding R16 (which spans 1 and 2). Any ideas anyone? Clearly there is a short
                                                        > somewhere, and not a bad chip after all.
                                                        >


                                                        I do not remember you giving the voltages you see on this chip.

                                                        73 Alan G4ZFQ
                                                      • wfahle
                                                        I am giving continuity checks now. I was reading 5v on pin 1, which was the original problem that made me suspect the chip was bad. In fact it looks like R15
                                                        Message 27 of 28 , Nov 3, 2012
                                                        • 0 Attachment
                                                          I am giving continuity checks now. I was reading 5v on pin 1, which was the original problem that made me suspect the chip was bad. In fact it looks like R15 is shorted to ground between it and C6+. That is not indicated in the schematic, so I'm now pulling R15.

                                                          --- In softrock40@yahoogroups.com, "Alan" <alan4alan@...> wrote:
                                                          >
                                                          >
                                                          > ----- Original Message -----
                                                          > Subject: [softrock40] Re: Bad chip? Not that one, in any case.
                                                          >
                                                          >
                                                          > > It indicates 5v on pin 1, Just like the other one in that respect. With power off, I'm currently reading 20.9 Kohms between pin 1
                                                          > > and pin 8, which when reviewing the schematic doesn't seem right. In fact the other dual op-amp which seems wired similarly is an
                                                          > > open circuit between those pins, giving me more confidence that this is the problem. I'm reading 11Kohms between 8 and 2 on U6,
                                                          > > which is probably where the 20.9 is coming from adding R16 (which spans 1 and 2). Any ideas anyone? Clearly there is a short
                                                          > > somewhere, and not a bad chip after all.
                                                          > >
                                                          >
                                                          >
                                                          > I do not remember you giving the voltages you see on this chip.
                                                          >
                                                          > 73 Alan G4ZFQ
                                                          >
                                                        • wfahle
                                                          Found the problem. See other thread.
                                                          Message 28 of 28 , Nov 3, 2012
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                                                            Found the problem. See other thread.

                                                            --- In softrock40@yahoogroups.com, "wfahle" <billfahle@...> wrote:
                                                            >
                                                            > I am giving continuity checks now. I was reading 5v on pin 1, which was the original problem that made me suspect the chip was bad. In fact it looks like R15 is shorted to ground between it and C6+. That is not indicated in the schematic, so I'm now pulling R15.
                                                            >
                                                            > --- In softrock40@yahoogroups.com, "Alan" <alan4alan@> wrote:
                                                            > >
                                                            > >
                                                            > > ----- Original Message -----
                                                            > > Subject: [softrock40] Re: Bad chip? Not that one, in any case.
                                                            > >
                                                            > >
                                                            > > > It indicates 5v on pin 1, Just like the other one in that respect. With power off, I'm currently reading 20.9 Kohms between pin 1
                                                            > > > and pin 8, which when reviewing the schematic doesn't seem right. In fact the other dual op-amp which seems wired similarly is an
                                                            > > > open circuit between those pins, giving me more confidence that this is the problem. I'm reading 11Kohms between 8 and 2 on U6,
                                                            > > > which is probably where the 20.9 is coming from adding R16 (which spans 1 and 2). Any ideas anyone? Clearly there is a short
                                                            > > > somewhere, and not a bad chip after all.
                                                            > > >
                                                            > >
                                                            > >
                                                            > > I do not remember you giving the voltages you see on this chip.
                                                            > >
                                                            > > 73 Alan G4ZFQ
                                                            > >
                                                            >
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