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Re: Troubleshooting RXTX 6.3

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  • g8xul
    Dear All, Thanks to everyone that s helped with this. The good news is that I can at last put this (long) thread to bed, and start getting some sleep. The
    Message 1 of 29 , Oct 1, 2008
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      Dear All,

      Thanks to everyone that's helped with this. The good news is that I
      can at last put this (long) thread to bed, and start getting some
      sleep. The bad news is I'm not sure of the solution. I tried 3
      things:

      1. Used a BS170 from a different source. (sorry Tony - no slur
      intended, just an observation:-)
      2. I tested with the RX BPF installed.
      3. I wrapped the legs of the Q7 FET together with wire before
      installing it to absolutly rule out an ESD problem.(Are these devices
      really a problem? To kill Q7 3 out of 3 times whilst Q8 survives is
      some chance.)

      Anyway - PTT and RX switching now work as expected.

      I'd be interested on any comments as to running the board without
      RXBPF. I won't be doing it till I learn better.

      Phew.

      73,Dave, G8XUL


      --- In softrock40@yahoogroups.com, "g8xul" <dave.james@...> wrote:
      >
      > I'm having trouble with the simplest element of the RXTX6.3
      > transmitter section and would appreciate some help before I start
      > pulling out components.
      >
      > The RX seems to work fine. I've checked soldering and component
      > values under magnification. I used good ESD practice throughout
      > construction.
      >
      > The problem is with the PTT section. Construction of the main
      board
      > is complete and I'm testing without the PA daughter board
      installed.
      > My original problem was that when testing the PA module The current
      > draw exceeded my 150mA current limit, knocking the supply voltage
      > down to a couple of volts. I decided to check the voltages at J1 /
      > J2 before faulting the PA board.
      >
      > On power up the current draw is ~95mA @ 7.047 center frequency.
      With
      > a DMM I measure:
      >
      > PTT IN 0V
      > /PTT IN ~10.5V
      > S12V 0V
      >
      > PTT IN was then connected to 12V (Cathode D1). Readings now:
      >
      > /PTT IN 0V
      > S12V ~11.8V
      >
      > PTT IN back to 0V (connected to ground). Readings now:
      >
      > /PTT IN ~ 5.8V
      > S12V ~11.8V
      >
      > S12V seems to have 'latched' at 11.8V. It remains at 11.8V
      > indefinately - irrespective of changes to PTT untill the power is
      > removed. The readings above can then be reproduced.
      >
      > Should S12V not follow PTT? Why does /PTT IN reduce to 5V'ish (the
      > value given in the detailed contruction notes)?
      >
      > Any help much appreciated.
      >
      > 73, Dave
      >
    • singhpk99
      hi Dave, Please wire a zener between the Gate and source on the bs170s to prevent further burnups. zener voltage should be 12 volts 400mw 73s push ab2xf
      Message 2 of 29 , Oct 1, 2008
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        hi Dave,

        Please wire a zener between the Gate and source on the bs170s
        to prevent further burnups.

        zener voltage should be 12 volts 400mw

        73s
        push
        ab2xf

        --- In softrock40@yahoogroups.com, "g8xul" <dave.james@...> wrote:
        >
        > Dear All,
        >
        > Thanks to everyone that's helped with this. The good news is that I
        > can at last put this (long) thread to bed, and start getting some
        > sleep. The bad news is I'm not sure of the solution. I tried 3
        > things:
        >
        > 1. Used a BS170 from a different source. (sorry Tony - no slur
        > intended, just an observation:-)
        > 2. I tested with the RX BPF installed.
        > 3. I wrapped the legs of the Q7 FET together with wire before
        > installing it to absolutly rule out an ESD problem.(Are these devices
        > really a problem? To kill Q7 3 out of 3 times whilst Q8 survives is
        > some chance.)
        >
        > Anyway - PTT and RX switching now work as expected.
        >
        > I'd be interested on any comments as to running the board without
        > RXBPF. I won't be doing it till I learn better.
        >
        > Phew.
        >
        > 73,Dave, G8XUL
        >
        >
        > --- In softrock40@yahoogroups.com, "g8xul" <dave.james@> wrote:
        > >
        > > I'm having trouble with the simplest element of the RXTX6.3
        > > transmitter section and would appreciate some help before I start
        > > pulling out components.
        > >
        > > The RX seems to work fine. I've checked soldering and component
        > > values under magnification. I used good ESD practice throughout
        > > construction.
        > >
        > > The problem is with the PTT section. Construction of the main
        > board
        > > is complete and I'm testing without the PA daughter board
        > installed.
        > > My original problem was that when testing the PA module The current
        > > draw exceeded my 150mA current limit, knocking the supply voltage
        > > down to a couple of volts. I decided to check the voltages at J1 /
        > > J2 before faulting the PA board.
        > >
        > > On power up the current draw is ~95mA @ 7.047 center frequency.
        > With
        > > a DMM I measure:
        > >
        > > PTT IN 0V
        > > /PTT IN ~10.5V
        > > S12V 0V
        > >
        > > PTT IN was then connected to 12V (Cathode D1). Readings now:
        > >
        > > /PTT IN 0V
        > > S12V ~11.8V
        > >
        > > PTT IN back to 0V (connected to ground). Readings now:
        > >
        > > /PTT IN ~ 5.8V
        > > S12V ~11.8V
        > >
        > > S12V seems to have 'latched' at 11.8V. It remains at 11.8V
        > > indefinately - irrespective of changes to PTT untill the power is
        > > removed. The readings above can then be reproduced.
        > >
        > > Should S12V not follow PTT? Why does /PTT IN reduce to 5V'ish (the
        > > value given in the detailed contruction notes)?
        > >
        > > Any help much appreciated.
        > >
        > > 73, Dave
        > >
        >
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