Harman kardon pop sound issue?

[kuer]

PM665, very nice amp. But when I volume down to lowest level, there is a pop sound on the left speaker.

And, when I push the " bass contour" button, there is a huge pop sound on the left speaker too. Seems the right channel is ok.

I cleaned up all buttons, should be ok.

What happened to it? checked online, no answer.

Thank you very much.

 

[JonSnell Electronic]

Is C909 leaky?

 

[DF96]

Dropping into or out of parasitic oscillation somewhere?

 

[amapolasola]

I've the same problem about "bass contour"...

Maybe it's the push button is out ?

I put some contact cleaner, put on closed pot or closed componant ; it's like to cook in a wok with big hole you know lol


Any idea ?

 

[sgrossklass]

Leaky coupling capacitor(s). Bad contact on the actual switch clearly won't help either.

Is it this very same model? Then my candidates would be C507, C909, C901 roughly in that order. I wouldn't trust a 30-year-old 10µ/16 that has always remained actively discharged very far at this point. The latter two you may be able to replace with film caps (rated maybe 25 V up), assuming the space is there, they are probably tiny.

 

[amapolasola]

oh ok thanx ; "Leaky coupling capacitor(s"
yes it's the same model ; pm665 ...
i have to remove c507, c909 c901

...but i have to renew all capacitors too ! It will be better...