Cr-200E distortion on left channel

[Gertjan90]

Hi guys,

I've recently been gifted a near mint looking Yamaha Cr-200e receiver with a small issue.
My goal is to turn this one into a nice looking bedroom unit, but I'll have to fix it first.
As I'll be ordering some parts for other amps soon, I thought now is the time to tackle this one as well and do a recap.

On to the problem:
The left channel will periodically sound distorted, as if no high frequencies reach the speaker. At first I thought I had blown my tweeter.. ( but I don't play my music loud so)
This will mostly happen after about an hour of playing, but sometimes it will pop up randomly.

I've deoxited(?) all switches already, and there are no obviously damaged parts inside.

Does anybody have an idea what I should be looking for, so I can start troubleshooting?
In the meantime, I'll look over the solder joints to see if they may be at fault.

It's a sweet sounding little amp with a great tuner, not to mention it looks gorgeous in it's wooden case, so I'm going to try my best at repairing this one.

Any help is appreciated!

 

[avionic]

When it acts up. exercise the with the speaker select switch as well as the rest of the switches and controls. It sounds like a dirty switch. But it could also be and issue with C419/420 the output coupling capacitors. Or it could also be a cold solder connection.

 

[Gertjan90]

I'm touching up some solders as we speak. They're not really bad, but they look don't 'nice' either. I'll do some testing after and test the controls.
Will report back.

 

[clinic-audio]

Fuse out on the distorded channel

 

[Gertjan90]

Hmm, shouldn't the sound cut out completely when the fuse is blown?

Anyway, the unit is playing fine right now, the only thing I can remark on is that when I turn the balance knob all the way to the right, everything sound fine (on fm mono), but when I turn it all the way to the left, some of the higher notes tend to disappear.
The sound from the left channel only is a bit 'muffled'. But even a tiny bit more balance towards the right will bring back the high notes.

At the moment, there is no distortion or popping, though.

 

[Gertjan90]

Quick update:
The balance issue is fixed now.
I've replaced the power supply and output coupling cap (?) with new ones of the same value.
Both channels now sound equally strong when turning the balance knob.
I'm going to let it run for a couple of hours to see is the left channel holds up now.