I have made significant progress, I hope, with my 516s
intermittent transmit problem.
I began the search for a solution at the output of the
?RF PWB TX Section?. I put a scope on the collector
of Q37 and monitored the output. (As an aside ? since
I had done a LP filter repair on the 516 I anticipated
that the output problem would be ?downstream? on the
Final PA board.) Well surprise ? when the TX failed I
had no RF output from Q37.
Next I moved to connector U7 and the TX connection on
pin #7. This is where the problem got interesting.
When the TX failed the output of pin #7 also failed.
So I thought I?d move on to the Logic board (shudder).
First, however, I loosened the 5 screws holding the
RF PWB TX Section board and slowly moved around the
board pushing on it with an insulated tuning tool.
Suddenly the rig came back to life.
I removed the RF PWB TX Section board and resoldered
the 3 multi-pin headers, RF connectors and any of the
larger components I could get access to. I then
turned the rig over and resoldered the mating headers
on the Logic Subassembly board.
I cleaned the mating headers with some DeOxit and
reassembled the rig. Unfortunately there was no
obvious failure found BUT the 516 has been on and off
several times in the last 36 hours and has NOT failed.
Hopefully I?ve solved the problem.
73,
Rick
VE7TK
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