Sony ST-A35 Weak Channel

Hi. I recently got a St-A35 Tuner which seems to be a pretty neat little analog tuner. The problem is that one channel is weak. I tried swapping cables around and changing inputs on the pre-amp and whatnot, but no dice. It's definitely a problem with the tuner.

I took the top off and everything looks super clean. No dust build up, no cruddy looking resistors and no visibly leaking caps.

I put a little fader lube on the tuner shaft since that seems to magically fix weird tuners sometimes, but no change on this one.

Having a little trouble finding the service manual, so I guess that is step one.

Any ideas on where I should start on tracking down the fault? I have a multimeter and that's about it.
 
Well, if the weak channel persists even for AM (or monophonic FM), that should narrow down the possibilities to whatever circuitry is downstream of the detectors.

hifiengine.com lists schematics and a service manual for something called ST-A35L. They're shown as being in French, but the schematic shouldn't be too language-specific.

Have you tried fiddling with the switches? I'm sure some of the switches handle audio signals, and dirty contacts are a perennial source of weak-signal problems.

Good luck,

chazix
 
I did de-oxit the switches which didn't seem to help.

Thanks for the suggestion on AM. I'll give that a try and see if I can narrow it down to a specific section of the boards.

The one FM channel sounds great and the reception on this tuner is pretty strong. Much better than my receivers.
 
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