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-   -   sugden a28b (http://www.diyaudio.com/forums/solid-state/134003-sugden-a28b.html)

Sjaak 29th November 2008 07:07 PM

sugden a28b
 
Hello DIY'ers,

Can someone tell me what could be wrong with my sugden A28B?
There is noise in the left channel when the volume control is operated. I replaced the potentiometer (ALPS) but the problem is still there. I have no schematic so it is difficult to find the problem.
Thank you for any advice!
Sjaak

Rikard Nilsson 29th November 2008 08:59 PM

Noise from a potentiometer can origin from DC voltage across it. That in turn may be the result of a shorted electrolytic cap, or an DC operating point way off.

But a schematic would help a lot.

Sjaak 30th November 2008 12:11 PM

Thank you Rikard,
So if DC is over the potentiometer I have to search for a short capacitor in the pre amp stage only?

Rikard Nilsson 30th November 2008 01:58 PM

I think so, or something else that might cause a stage to operate at the wrong DC level. I canīt imagine there should be any DC voltage across the pot. You could always measure the working channel to see if there is any DC.

If there are tantal caps these are the ones to check. They are known to short.


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