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OT2 Proto B NMJ221D VCC

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  • James Ewen
    Scott, What do you think about this problem... I get no decode on my OT2 Proto B. I ve traced it back to the 2211 demodulator section. There should be +5v on
    Message 1 of 8 , Jun 22, 2007
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      Scott,

      What do you think about this problem...

      I get no decode on my OT2 Proto B. I've traced it back to the 2211
      demodulator section. There should be +5v on pin 1, but it sits at
      +0.4v. I finally got around to poking around on the PCB with the top
      and bottom view images I created out of the Gerber files you posted. I
      have +5v at pin 9 of the micro, but +0.4v at pin 1 on the 2211.

      There is a trace that runs directly from pin 9 of the micro to pin 1
      of the 2211, with C12 at the micro, and C4 at the 2211 end of the
      trace filtering the voltage.

      When the OT2 powers up, D4 lights green, goes dark, lights red, and
      then goes dark. During this cycle, I can see +2v on pin 1 of the 2211
      whenever D4 is lit up.

      If I pull the 2211 out of it's socket, I see +5v on pin 1. I'm
      thinking I have a blown 2211 chip.

      James
      VE6SRV
    • Ian ZL1VFO
      ... James, can you post those top & bottom images somewhere (preferably in PNG or GIF image format), perhaps in the Yahoo Groups files section). I have a copy
      Message 2 of 8 , Jun 23, 2007
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        > 1. OT2 Proto B NMJ221D VCC
        > Posted by: "James Ewen" ve6srv@... james_ewen
        > Date: Fri Jun 22, 2007 12:54 pm ((PDT))

        > Scott,

        > What do you think about this problem...

        > I get no decode on my OT2 Proto B. I've traced it back to the 2211
        > demodulator section. There should be +5v on pin 1, but it sits at
        > +0.4v. I finally got around to poking around on the PCB with the top
        > and bottom view images I created out of the Gerber files you posted. I
        > have +5v at pin 9 of the micro, but +0.4v at pin 1 on the 2211.

        James, can you post those top & bottom images somewhere (preferably in
        PNG or GIF image format), perhaps in the Yahoo Groups files section).
        I have a copy of ot2m_proto_c_bottom.png and ot2m_proto_c_top.png but
        the PCB tracks may have moved a bit between the 'C' and the 'B'
        version that you have.

        I'll try and trace out the path of that missing 5V and make a list of
        points to check. I suspect it's more likely a break in the track
        somewhere, probably next to a pad or perhaps a plated-thru hole didn't
        get plated-thru, so something simple that a touch of hot solder should
        fix. I suspect your 2211 is probably ok (although I could always be
        wrong, hi!)

        > There is a trace that runs directly from pin 9 of the micro to pin 1
        > of the 2211, with C12 at the micro, and C4 at the 2211 end of the
        > trace filtering the voltage.

        > When the OT2 powers up, D4 lights green, goes dark, lights red, and
        > then goes dark. During this cycle, I can see +2v on pin 1 of the 2211
        > whenever D4 is lit up.

        > If I pull the 2211 out of it's socket, I see +5v on pin 1. I'm
        > thinking I have a blown 2211 chip.

        Since there should only be a low resistance copper track between pin 9
        of the micro to pin 1 of the 2211, it should stay pretty close to 5V (
        say within +/- 0.2 V ) regardless of LEDs turning on & off...

        Also, it pays to check the Gnd / 0V points are all joined together with a
        ohm-meter too; weird things can start happening if you're missing a ground.

        > James
        > VE6SRV


        73,
        Ian ZL1VFO
      • zl1vfo
        ... Mmm, that was quick, James!
        Message 3 of 8 , Jun 23, 2007
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          <Ian ZL1VFO wrote:>
          >
          > James, can you post those top & bottom images somewhere (preferably in
          > PNG or GIF image format), perhaps in the Yahoo Groups files section).

          Mmm, that was quick, James!

          <http://groups.yahoo.com/group/tracker2/files/OT2ProtoB/OT2a.png>
          <http://groups.yahoo.com/group/tracker2/files/OT2ProtoB/OT2b.png>
          <http://groups.yahoo.com/group/tracker2/files/OT2ProtoB/OT2dualcomp.png>
          <http://groups.yahoo.com/group/tracker2/files/OT2ProtoB/OT2dualsold.png>

          Thanks,
          I'll d/l them & have a look...

          73, Ian ZL1VFO
        • James Ewen
          ... Yup, there are minor differences, which is why I pestered Scott for the info. The images are on the yahoogroups files section. ... Have a look at
          Message 4 of 8 , Jun 23, 2007
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            On 6/23/07, Ian ZL1VFO <zl1vfo@...> wrote:

            > James, can you post those top & bottom images somewhere (preferably in
            > PNG or GIF image format), perhaps in the Yahoo Groups files section).
            > I have a copy of ot2m_proto_c_bottom.png and ot2m_proto_c_top.png but
            > the PCB tracks may have moved a bit between the 'C' and the 'B'
            > version that you have.

            Yup, there are minor differences, which is why I pestered Scott for
            the info. The images are on the yahoogroups files section.

            > I'll try and trace out the path of that missing 5V and make a list of
            > points to check. I suspect it's more likely a break in the track
            > somewhere, probably next to a pad or perhaps a plated-thru hole didn't
            > get plated-thru, so something simple that a touch of hot solder should
            > fix. I suspect your 2211 is probably ok (although I could always be
            > wrong, hi!)

            Have a look at power.png. I have the +5v trace highlighted, and
            labelled as to where my 5 volts turns into 0.4 volts. If I pull the
            2211, the 0.4 volt point reads 5 volts. Perhaps I have a bad solder
            joint in a poorly plated hole causing high resistance, dropping my
            voltage along that trace.

            James
            VE6SRV


            >
            > > There is a trace that runs directly from pin 9 of the micro to pin 1
            > > of the 2211, with C12 at the micro, and C4 at the 2211 end of the
            > > trace filtering the voltage.
            >
            > > When the OT2 powers up, D4 lights green, goes dark, lights red, and
            > > then goes dark. During this cycle, I can see +2v on pin 1 of the 2211
            > > whenever D4 is lit up.
            >
            > > If I pull the 2211 out of it's socket, I see +5v on pin 1. I'm
            > > thinking I have a blown 2211 chip.
            >
            > Since there should only be a low resistance copper track between pin 9
            > of the micro to pin 1 of the 2211, it should stay pretty close to 5V (
            > say within +/- 0.2 V ) regardless of LEDs turning on & off...
            >
            > Also, it pays to check the Gnd / 0V points are all joined together with a
            > ohm-meter too; weird things can start happening if you're missing a ground.
            >
            > > James
            > > VE6SRV
            >
            > 73,
            > Ian ZL1VFO
            >
            >
          • zl1vfo
            ... Yep, I see that trace in power.png - it s not that long so the problem shouldn t be too hard to locate.. With the board powered up & the 2211 connected
            Message 5 of 8 , Jun 23, 2007
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              >
              > Have a look at power.png. I have the +5v trace highlighted, and
              > labelled as to where my 5 volts turns into 0.4 volts. If I pull the
              > 2211, the 0.4 volt point reads 5 volts. Perhaps I have a bad solder
              > joint in a poorly plated hole causing high resistance, dropping my
              > voltage along that trace.
              >
              > James
              > VE6SRV
              >

              Yep, I see that trace in power.png - it's not that long so the
              problem shouldn't be too hard to locate..

              With the board powered up & the 2211 connected normally, establish
              that you have that +5v on both top and bottom of that C12 point, and
              then do the same with the C4 point.
              The voltage (5 or 0.4) should match top and bottom of the holes, and
              also the component leg.
              If it's different, your problem's right there somewhere.

              Now assuming one end of that track has power and the other end
              doesn't, work you way along the track from the C12 point 1/4 inch at a
              time until the voltage dissappears. If the board has a protective
              coating over it, you might have to pierce it with a compass point or a
              push pin or some other sharp pointy object so you make contact with
              the copper track underneath.

              Once you've found the point between 'volts' and 'no volts', stick the
              board in front of a really strong light, and you should see the PCB
              track silhouetted as the light passes through the PCB, but not the
              copper area. Unless of course the other side of the PCB has a lot of
              copper covering it. Anyway, have a good look with a strong magnifying
              glass or jeweller's loupe and witha bit of luck you should see the break.

              Then you can remove a small amount of protective coating (if present)
              and solder a link over the top of the break...

              See how you go...

              73,
              Ian ZL1VFO
            • P. Suryono Adisoemarta
              ... You might already do this, but if not reflow the solders and see if that helps. Otherwise, lift that Vcc leg off of the socket, and hook it up straight to
              Message 6 of 8 , Jun 23, 2007
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                James Ewen wrote:
                >
                > Have a look at power.png. I have the +5v trace highlighted, and
                > labelled as to where my 5 volts turns into 0.4 volts. If I pull the
                > 2211, the 0.4 volt point reads 5 volts. Perhaps I have a bad solder
                > joint in a poorly plated hole causing high resistance, dropping my
                > voltage along that trace.
                >
                > James
                > VE6SRV
                >
                >

                You might already do this, but if not reflow the solders and see if that
                helps.
                Otherwise, lift that Vcc leg off of the socket, and hook it up straight
                to a 5v source, and see if that helps. If not then you might have a
                shorted 2211 (might blew the voltage regulator, probably temporarily use
                an amp meter in between to double-check the current, should be around 15
                mA or less to the 2211 chip).

                This solution is similar to my solution on the non-decoding 2211 Proto
                B, due to the data input pin is shorted to ground:
                http://groups.yahoo.com/group/tracker2/message/1651
                that I posted 2 months ago.

                73 de Paulus
              • James Ewen
                ... Reflow didn t work, but I sucked all the solder off of the pad at C4 after poking along the trace determined that I had 5v right up to the pad. The trace
                Message 7 of 8 , Jun 25, 2007
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                  On 6/23/07, P. Suryono Adisoemarta <yono_adisoemarta@...> wrote:

                  > You might already do this, but if not reflow the solders and see if that
                  > helps.

                  Reflow didn't work, but I sucked all the solder off of the pad at C4
                  after poking along the trace determined that I had 5v right up to the
                  pad. The trace ended just before the pad for C4. There was a little
                  bit of trace sticking out from under the solder mask, the 0.4v was
                  probably leaking through other components. I scraped back the mask off
                  of the trace and bridged the gap with a single strand of wire.

                  I now have decode... Some days you just have to wonder where your
                  brain goes. It's good to have a resource like this to give you a knock
                  up side the head once and a while!

                  Now for even more playing.

                  James
                  VE6SRV
                • Ian ZL1VFO
                  ... Ah, I ve seen this happen before on PCBs (not Scott s thou ), and on one s I ve fixed it does seem a weak point is right where the pad and track meet.
                  Message 8 of 8 , Jun 27, 2007
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                    > 1a. Re: OT2 Proto B NMJ221D VCC
                    > Posted by: "James Ewen" ve6srv@... james_ewen
                    > Date: Mon Jun 25, 2007 7:21 am ((PDT))

                    > On 6/23/07, P. Suryono Adisoemarta <yono_adisoemarta@...> wrote:

                    >> You might already do this, but if not reflow the solders and see if that
                    >> helps.

                    > Reflow didn't work, but I sucked all the solder off of the pad at C4
                    > after poking along the trace determined that I had 5v right up to the
                    > pad. The trace ended just before the pad for C4.

                    Ah, I've seen this happen before on PCBs (not Scott's thou'), and on
                    one's I've fixed it does seem a weak point is right where the pad and
                    track meet. Great that you have it going now!

                    73, Ian ZL1VFO

                    > There was a little
                    > bit of trace sticking out from under the solder mask, the 0.4v was
                    > probably leaking through other components. I scraped back the mask off
                    > of the trace and bridged the gap with a single strand of wire.

                    > I now have decode... Some days you just have to wonder where your
                    > brain goes. It's good to have a resource like this to give you a knock
                    > up side the head once and a while!

                    > Now for even more playing.

                    > James
                    > VE6SRV
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