Help Please-Distortion in Rebuilt Amp


2002-05-18 10:01 pm
I have a distortion problem which I have isolated to one channel on my PCB. The amp is silent with no signal even when connected to an input(silent passage between speech/music). It is less noticeable at higher volumes and disappears when the power is turned off and the amp continues on the stored energy in the caps. I have tried different earthing including Star to no effect. Help please.
Hi Hifileslie,

With the power turned on, cross check voltage levels. You may find that at one point the voltage level of the bad side is not the same, or close to the voltage level of the same point on the good side.

Now, assuming this is solid state, then I would suspect a particular transistor, if you replaced all the transistors. Maybe it is either out of spec, or it is installed incorrectly. Could even be a bad bias diode.

Get a good transistor checker to check all of them (Radio Shack has a nice one for about 15 bucks. I think it also checks diodes).

I say this because you say that with power on full, it distorts, but with power off it sounds OK as the caps discharge. Therefore the suspected component is working OK within a certain voltage range, but not at full spec.

That is my 2 cents.