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Trouble-Shooting RX on my RXTX V6.2 40/30M Board

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  • R. R. Robson
    After finishing stuffing and wiring it, I tested the RX part of my board. Not too surprisngly, it came up a cropper, yielding the commonly lamented central
    Message 1 of 31 , Jul 23 9:32 AM
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      After finishing stuffing and wiring it, I tested the RX part of my board.  Not too surprisngly, it came up a cropper, yielding the commonly lamented central spike and outriders on Rocky's display.

      I tested what I could, using the notes from this forum.  The test results are in a PDF  on Cecil's website, and are summarized below:

      1.  Resistances tested out OK.  Power was 12.02 vdc (sans smoke) and VCC was 4.92 vdc.

      2.  LO signal seemed to make it ok into two out-of-phase signals at pins 2 and 14 of U7.

      3.  RX Mute was low at pins 1 and 15 of U7

      4.  Signal from T4 secondaries looked like LO noise (approx 60 mv) with dc voltages of 2.33 at each of pins 3, 6, 11, and 12 of U7

      5.  DC voltages at U7 pins 7 and 9 were 2.32 and 2.33; scope showed no signal

      6.  U8 voltages at pins 2, 3, 5, 6, and 7 were in the neighborhood of 2.33 vdc; pin 1 was curiously 2.07 vdc

      7.  Scope showed no signal at I and Q terminals

      Looks like it is time to call in the elmerian reserves. 

      Anyone care to peruse the results and suggest any strategies for me.  I, like so many others, refuse to give up.  Yea, verily, the spirit is willing but the flesh (between my ears) is weak!

      TX es 73 de Robby WB5RVZ

       

    • Russell Blair
      Bill, Sorry I was in meeting most of the day and will try to get to your request soon, However I was able to find last night what was my null on one side of
      Message 31 of 31 , Jul 31 5:07 PM
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        Bill, Sorry I was in meeting most of the day and will
        try to get to your request soon,
        However I was able to find last night what was my null
        on one side of the Rocky display, I had been on RTTY
        the night before, on the same soundcard, and what I
        forgot to do was put the soundcard Mic-input back to
        line-input,the Mic input is mono, after changeing it
        to line-in-put I now have a full band view.

        Russell

        --- Bill Dumke <billd@...> wrote:

        > The peak to peak is not so important as the low and
        > high levels the
        > waveform reaches. It needs to be centered on 2.5
        > vdc for the flip flop
        > to clock properly. What are the high and low
        > voltages the waveform
        > reaches. You will have to set the channel on the
        > scope to DC rather
        > than AC coupling and then make sure it reads zero
        > with no signal applied.
        >
        > Bill wa9pwr
        >
        > Russell Blair wrote:
        > > My test equipment is a Tektronix TDS 3044 last Cal
        > > 3/12/07 and a Tektronix Tx3 Multi meter Cal
        > 3/12/07.
        > >
        > > Bill, I check at x4 with the x1 being 40m cystal
        > the
        > > reading was 2.20v Pk-Pk 7.020Mhz and with x2 the
        > 30m
        > > cystal it was 1.05v Pk-Pk 10.130Mhz.
        > >
        > > X1=40m
        > > X2=30m
        > >
        > > Ok some more voltage Pk-Pk reading U6 pin 6=5.24v
        > Pin
        > > 8=5.24v with X2, U6 pin 6=5.22v pin 8=5.22v with
        > X1,
        > > pin 5=5.20v X1-X2, pin 9=5.20v X1-X2.
        > >
        > > Not Pk-Pk U7 pin 7=2.39v X1-X2, pin 9=2.39v X1-X2.
        > >
        > > Russell
        > >
        > > --- Bill Dumke <billd@...> wrote:
        > >
        > >
        > > ---------------------------------
        > >
        > > Russell,
        > >
        > > Check the Jumper x4 with a scope and see what kind
        > of
        > > a voltage swinghe is getting on the crystal
        > oscillator
        > > output. Mine was only goingfrom 2.5 v to 5.0 v.
        > It
        > > was due to a bad IC U5. After I got thatreplaced,
        > the
        > > voltage swing was about 1 volts to 5 volts, where
        > > itshould be.
        > >
        > > Receiver works great, except for that huge spike
        > with
        > > 60 Hz coveringabout 20 or more kHz of the band. I
        > am
        > > thinking of adding a 1:1 balunat the antenna
        > connector
        > > for that. Running a ground mounted verticalhere.
        > > With the earlier SoftRock receivers you could
        > isolate
        > > theantenna ground from the chassis ground by the
        > input
        > > transformer. Idon't see any spike that way. But
        > that
        > > won't work for a transceiverlike this. But I
        > should
        > > be able to add an external 1:1 balun.
        > >
        > > Bill wa9pwr
        > >
        > > Russell Blair wrote:
        > > Hi to all, This is Rusell and I have got Rob's
        > > unitRx'ing now, the supply is (12)vdc wall unit,
        > at U4
        > > pin3 I have 4.92 vdc. That put 4.92 vdc on pins 8
        > of
        > > U5and on pins 3 and 5 of U8 is 2.56 vdc, now on
        > pins
        > > 1and 7 I have 2.35 vdc. That also puts 2.56 on
        > > thecenter tap on T4 that puts 2.54 on U7 pins
        > > 3,6,11,12on pins 1,15 is .5 vdc. I had to clean
        > up
        > > the bottomof the board, I redone T4 onlt because I
        > was
        > > unable totell if is was correct or not. With
        > Rocky3.2
        > > I nowhave audio, and been copying CW and seeing
        > othe
        > > modes.On one side of the Rocy display it has a
        > null
        > > abouthalf way cross the band, it just goes flat
        > and
        > > pics upand the end of the band, I need to do some
        > > checkingaround U5 and U6 with a scope and look at
        > the
        > > I&Qdata, voltage on pins, and see why it doing
        > that.
        > > So Ihave more to do with this unit.Russell
        > NC5O---
        > > Alan <g4zfq@...> wrote:
        > >
        > > ----- Original Message ----- From: "R. R. Robson"
        >
        > >
        > > Pin 3 of the 5 volt regulator actually reads out
        >
        > >
        > > as 4.92 vdc on my DMM.
        > >
        > > This SEEMS a bit low but we are getting close
        > > totolerance limits.The DVM may read a little low
        > and
        > > the 5 volt IC maybe a little low.From the 4.92 we
        > > might expect U8 pins 3&5 to read2.46 volts.As you
        > have
        > > said a digital display gives precisereadings that
        > are
        > > notnecessarily accurate.You have already confirmed
        > > that the current taken bythe unit is correct
        > sothere
        > > is no excessive draw to pull the voltage down.We
        > wait
        > > to hear what Russell finds.73 Alan G4ZFQ
        > >
        > > ================= IN GOD WE TRUST !
        > =================
        > > Russell Blair QTH ========= Richardson Tx CALL
        > > ========= NC5O GRID ========= EM12px FH#
        > ==========
        > > 300 DOS# ========= 470 =================
        > >
        >
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        > >
        > >
        > > =================
        > > IN GOD WE TRUST !
        > > =================
        > > Russell Blair
        > > QTH ========= Richardson Tx
        > > CALL ========= NC5O
        > > GRID ========= EM12px
        > > FH# ========== 300
        > > DOS# ========= 470
        > > =================
        > >
        > >
        > >
        > >
        >
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        =================
        IN GOD WE TRUST !
        =================
        Russell Blair
        QTH ========= Richardson Tx
        CALL ========= NC5O
        GRID ========= EM12px
        FH# ========== 300
        DOS# ========= 470
        =================



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