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Topic: Old amplifier: low humming on one output, "bleeds through" to others too (Read 296 times) previous topic - next topic
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Old amplifier: low humming on one output, "bleeds through" to others too

It's been 5 years since I was able to get my old Soviet amplifier working with your help. It hasn't popped a fuse since, but recently I noticed a low humming noise on the left channel. This hum is always present on all input channels to a certain degree except one, where the noise is much louder and is present on both channels.

I have tried disconnecting everything but the speakers, but the hum is still present. If anything, disconnecting the input cables actually makes the hum louder. What could be causing this?

I have the full schematic here. I've marked the input selector part of the schematic, do tell if you need more info.

 

Re: Old amplifier: low humming on one output, "bleeds through" to others too

Reply #1
On possible reason and the most probable is dry electrolytic caps. You ned to test them.

 
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