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Re: Good news, then not so good...

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  • Bill P.
    Yes, around 90ma draw on receive is about right. It would be very hard to help at this point, leave the power on and try to find a warm part. After that it
    Message 1 of 6 , Feb 28, 2009
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      Yes, around 90ma draw on receive is about right. It would be very
      hard to help at this point, leave the power on and try to find a warm
      part. After that it takes some real problem solving techniques that
      are hard to cover here.

      I just finished 2 hours of contacts making the board not-cold to
      touch, nothing on the bottom is warm, only the top area around R19 and
      the PTT and serial area are slightly warm. Bill k6acj

      --- In softrock40@yahoogroups.com, "Mike" <mike@...> wrote:
      > --- In softrock40@yahoogroups.com, "Bill P." <k6acj@> wrote:
      > >
      > > Something should be warm if the measurements are correct.
      > The normal current draw -was- 90 Ma; It is now 160 Ma. (Not too much
      > current...)
      > Remove the
      > > PA module does the currant draw change? Check the PA heat sink and
      > > measure the voltage drops across R210 & R211, the 2.1 ohm source
      > > resistors on each FET. Shoud be 55mv drop. Maybe one of the
      > > resistors shows higher drop therefore the FET associated FET is bad.
      > No added current is being drawn by the PA/Filter.
      > (The 160 Ma current draw remains the same, no matter if the receive
      > bandpass filters or if the PA/Filter boards are installed or not.
      > >
      > > If the SR is still drawing high currant without the PA module, then it
      > > gets more difficult but suspect a solid state device internally
      > > shorting to ground if there are no circuit board shorts.
      > This is what I am afraid of...
      > A bit of history:
      > - The unit initially drew about 90 Ma in receive.
      > - It now draws about 160 Ma in receive.
      > - The PA/Filter and the receive bandpass boards are NOT installed.
      > - I have never tried to transmit, yet.
      > - The normal QSD and QSE signals are still present on the board.
      > Using PowerSDR, the NOISE FLOOR was really, REALLY high!
      > - The noise floor was well above S-9, even if the antenna inputs were
      > shorted together.
      > - The unit DID work at first. (For several hours.)
      > - When the unit did work, BOTH of the PA/filter boards were installd.
      > - The unit did receive, but it took a very BIG (S-9 + 10 to 20 dB)
      > - I had a good I/Q output from the RXTX output to the computer, when
      > it worked.
      > - I no longer have the I/Q output, and PowerSDR is showing a very LOW
      > level in the panoramic adapter.
      > >
      > > 80/40 are sometimes dead in the evening , listen for WWV on 2.5, 5 or
      > > 10Mhz or put your commercial gear on low power and perform a
      > transmission.
      > If I attach an antenna, I hear (and SEE) nothing.
      > If I inject a signal from my service monitor, I hear (and see) nothing.
      > >
      > > Sometimes the Software does not start correctly or if USB there can be
      > > a problem, do a cold boot with all connections in place.
      > No USB is being used at this time. I have only POWER, ANTENNA and the
      > I/Q wires attached to the RXTX.
      > Major question: Dare I use a DVM to look for shorts? Or, will this
      > do damage to the ICs that are in place?????
      > Related question: How do I locate the short or added load? (To
      > resolve the issue.)
      > Thank you! -Mike- K0JTA
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