Help Troubleshoot Issues With Sony TA-AX390

[nsdigirolamo]

Hi AK - This is my first post so please let me know if there's anything missing or if it needs to go in a different section of the forum. I picked up a Sony TA-AX390 integrated stereo amplifier last spring and have had it for a few months now. I got it for a good deal alongside a separate tuner, cassette player, CD player and the service and user manuals. It works pretty well most of the time, but every once in a while the left channel becomes much quieter than the right and at lower volumes it will even cut out or sound distorted. Frustratingly, this seems to happen at random and I haven't been able to determine the cause.

I seriously suspect this is an issue with the amplifier and not any other part of my setup. I've tried different wires, speakers, and input sources and the issue persists regardless of whatever I'm using. I've tried opening the amp and cleaning the volume controls with Deoxit, but that didn't seem to do anything either. I've also found this video where the person is repairing the same model with a similar issue, but I'm having a hard time understanding how he's actually diagnosing the broken components other than just seeing if they're loose or not. I'm not super comfortable using a soldering iron, so I don't want to attempt to reproduce anything he's doing if my amp isn't actually broken in the same way.

Does anyone have any suggestions on how I can troubleshoot this issue? Is this even something worth fixing on my own? I've been engaging with this technology pretty casually up to this point so I don't really know how to even begin to approach something like this.

Thanks.

 

[avionic]

but every once in a while the left channel becomes much quieter than the right and at lower volumes it will even cut out or sound distorted. Frustratingly, this seems to happen at random and I haven't been able to determine the cause.

Dirty switch contacts or poor solder connections. Could be fouled protect relay contacts.

 

[nsdigirolamo]

Dirty switch contacts or poor solder connections. Could be fouled protect relay contacts.

What does "switch contacts" refer to here? Like physical switches I can press with my fingers, or is this a component of the amp? And do you have any advice on how I could identify poor solder connections or bad relay contacts? Are these something I could identify by sight or use a multimeter to test?