Noises Mini Aleph


2009-10-16 8:59 pm

I have a Mini Aleph with BriantGT PCBs.

It has been in service in my main system for years now.
Recently I am getting some random not too loud noises in one channel.
They sound a bit like a stylus scratching/jumping grooves. Or like a dying tube.
They come some time after turning on and they go away randomly (usually after a few seconds).
I have traced the noises down to the power amp (ie not spreakers, not the preamp - B1 btw)
As I said it is only one channel. I have a single power supply for both channels so it is not the PS either.
I suspected a cold joint so I resoldered the whole PCB but the problem is still there.

Not sure how to proceed as it is hard to measure something that goes away randomly.

My first guess would be the protection zeners at the input, so I will probably just replace them.

Has anybody any idea how to attack this? Anybody had similar issues?