14 Jul
2007
14 Jul
'07
2:18 p.m.
John,
The microphonics is caused by C19, C27 and C28 (.047uF 25V) and C50 and C51 (.022uF 25V).
I found the best way to isolate this is to inject a CW signal into the receiver, tune the signal in at the IF output using my TS-2000 in AM mode, and then listen to the audio output while lightly tapping each component one at a time.
According to my research, barium titanate, the base ceramic material for most ceramic SMD capacitors is inherently microphonic.
Juan