Re: click fix and squeal on transmit #ubitx

Don, ND6T
 

When the rig is not powered or in the receive mode there should be continuity from the Rx connection point to 12V. through relay K1 contacts 3 and 5. That is normal. The squeal is not!
First step in diagnosis is to check the voltage on the gate of Q3 when in transmit mode. It should be below 1 volt referenced to the ground connection on that board. If not, check to see that the ground connection there has the same potential as the ground plane of the BITX. Then track down the voltage discrepancy. The operation depends on Q3, acting as a gate, being turned off, thus opening that gate. If that gate is allowing the I/O (when in transmit, it is the microphone pre-amp output) to be leaking into the audio output then you will get enough feedback to oscillate. If the gate of Q3 is below 1 volt referenced to the source during transmit then Q3 may be bad. If there is voltage on the source, check your solder connections of R4.
Keep us informed, please. 73, -Don

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