Harman Kardon PM 620 oscillating

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Vix

Vix

Member
Joined 2003
Hi,

Yesterday a friend of mine brought me Harman Kardon PM 620 amp.

While the right channel works fine, the other one seems to be oscillating.

It plays music , although the sound is strange. It is twice as quiet, and somehow lack bass. Then, I noticed that the left channel produces a faint noise, which changes the pitch as I move the volume knob. At the pot zero position, the frequency is lowest. As I move the pot, the pitch increases...

I checked all connections, switches, looked for a bad solder, found nothing. Measured transistors, compared voltages on the left and right channel. Almost the same. I have no clue what could be causing the problem.

A hint would be appreciated.

Thanks a lot,

Vix
 
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