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Still having issues around the AC74 and possibly the LO Softrock RXTX

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  • Ross
    Ok, been working through this methodically for several days now trying to figure out why I m getting wrong voltage values at the AC74 pins. Getting 5v where
    Message 1 of 6 , May 23, 2014
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      Ok, been working through this methodically for several days now trying to figure out why I'm getting wrong voltage values at the AC74 pins.  Getting 5v where I'm supposed to be getting 2.5v.  I'll list the current voltages down below. 

      I purchased an inexpensive PC based oscilloscope to help me track down where things seem to be going wrong. It has it's limitations but it can show the LO's signal for me enough to know it's present.  The signal is getting to and past R13, it's getting TO R14 but it's attenuated to the point my oscilloscope can't detect.  Is the LO weaker than it's supposed to be?  I just can't figure out where the problem with voltages and signal attenuation.

      Here are the voltages at the various check points:

      R12 hairpin: 0v
      R13 hairpin: 2.5V
      R14 hairpin: 5V

      AC74
      p1: 5v
      p2: 5v
      p3: 2.5v
      P4: 5v
      P5: 5v
      p6: 5v
      p7: gnd
      p8: 5v
      p9: 5v
      p10: 5v
      p11: 2.5v
      p12: 5v
      p13: 5v
      p14: 5v

      attachment: png image oscilloscope captures for those that can't see inline images

      hairpin 13 image
      Hairpin_13

      hairpin 14
      Hairpin_14

      pin 4 Si570
      pin_4_Si570

      pin 6 Si570
      Pin_6_Si570

      pin 3 ac74
      pin_3_ac74

      pin 11 ac74
      pin_11_ac74

      Ross
      KD0VHN
    • Alan
      Original Message ----- Subject: [softrock40] Still having issues around the AC74 and possibly the LO Softrock RXTX ... Ross, Voltage readings are enough to
      Message 2 of 6 , May 23, 2014
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        Original Message -----
        Subject: [softrock40] Still having issues around the AC74 and possibly the LO Softrock RXTX


        > Ok, been working through this methodically for several days now trying
        > to figure out why I'm getting wrong voltage values at the AC74 pins.
        > Getting 5v where I'm supposed to be getting 2.5v. I'll list the current
        > voltages down below.
        >

        Ross,

        Voltage readings are enough to show the presence of signals.

        2V5 on the two pins used as inputs shows it is there.
        5V on the other pins means the IC is not working. Some should be 0V if some are 5V.
        Is the ground pin soldered correctly?
        Is it mounted correctly?

        If so, new IC required.

        73 Alan G4ZFQ


        >
        > Here are the voltages at the various check points:
        >
        > R12 hairpin: 0v
        > R13 hairpin: 2.5V
        > R14 hairpin: 5V
        >
        > AC74
        > p1: 5v
        > p2: 5v
        > p3: 2.5v
        > P4: 5v
        > P5: 5v
        > p6: 5v
        > p7: gnd
        > p8: 5v
        > p9: 5v
        > p10: 5v
        > p11: 2.5v
        > p12: 5v
        > p13: 5v
        > p14: 5v
        >
      • Alan
        Original Message ----- Subject: [softrock40] Still having issues around the AC74 and possibly the LO Softrock RXTX ... I just looked, pin3, 11 scope shots do
        Message 3 of 6 , May 23, 2014
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          Original Message -----
          Subject: [softrock40] Still having issues around the AC74 and possibly the LO Softrock RXTX


          >
          > I purchased an inexpensive PC based oscilloscope to help me track down
          > where things seem to be going wrong.

          I just looked, pin3, 11 scope shots do not support your voltage readings? Which is right?

          73 Alan G4ZFQ
        • Ross
          Alan, Yes, pin 7 is solid, I ve been using it for reg. ground on for the AC74 check. Looks like I ve got a bum AC74 IC. I was afraid that may be the case
          Message 4 of 6 , May 23, 2014
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            Alan,

            Yes, pin 7 is solid, I've been using it for reg. ground on for the AC74 check.  Looks like I've got a bum AC74 IC.  I was afraid that may be
            the case since I couldn't figure out anything else.  I should talk to 5 dash to get a replacement IC?

            Ross
            73s KD0VHN

            On 5/23/2014 6:44 AM, 'Alan' alan4alan@... [softrock40] wrote:
             


            Ross,

            Voltage readings are enough to show the presence of signals.

            2V5 on the two pins used as inputs shows it is there.
            5V on the other pins means the IC is not working. Some should be 0V if some are 5V.
            Is the ground pin soldered correctly?
            Is it mounted correctly?

            If so, new IC required.

            73 Alan G4ZFQ

            >


          • Ross
            Alan, Sorry, mislabeled a couple of captures. These are the actual captures from pin 3 & 11 respectively from AC74: AC_74 pin 3 AC74 pin 11 Ross
            Message 5 of 6 , May 23, 2014
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              Alan,

              Sorry, mislabeled a couple of captures.

              These are the actual captures from pin 3 & 11 respectively from AC74:

              AC_74 pin 3

              AC74 pin 11

              Ross



              On 5/23/2014 6:52 AM, 'Alan' alan4alan@... [softrock40] wrote:
               


              Original Message -----
              Subject: [softrock40] Still having issues around the AC74 and possibly the LO Softrock RXTX

              >
              > I purchased an inexpensive PC based oscilloscope to help me track down
              > where things seem to be going wrong.

              I just looked, pin3, 11 scope shots do not support your voltage readings? Which is right?

              73 Alan G4ZFQ


            • Alan
              Original Message ----- Subject: Re: [softrock40] Still having issues around the AC74 and possibly the LO Softrock RXTX ... Ross, I m still confused! Best stick
              Message 6 of 6 , May 23, 2014
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                Original Message -----
                Subject: Re: [softrock40] Still having issues around the AC74 and possibly the LO Softrock RXTX


                > Sorry, mislabeled a couple of captures.
                >
                > These are the actual captures from pin 3 & 11 respectively from AC74:
                >
                > AC_74 pin 3
                >
                > AC74 pin 11
                >

                Ross,

                I'm still confused!
                Best stick with the voltage readings:)

                Yes, Tony will send a replacement if you contact him.

                73 Alan G4ZFQ
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