Advice needed for vintage amp repair: one channel distortion

[Marshtech]

I would replace IC3 at this point.

[Pixel]

Pixel it's the same channel (left) that distorts when I feed tape in. BTW, before the latest replacement of C79, there was some very low sound on the left, now it is almost completely muted.

Thanks again!

I just wanted to make sure that we were working on the correct channel.

Do you still have the oscilloscope? If so you could see if there is good signal coming into the IC. Its great you have the good channel to compare to, but be careful not to touch more than one pin at a time on the ic with the oscilloscope probe.

I'm not convinced that the IC is bad yet. If you did something to make it go bad we should try to find out what that was or the replacement will just go bad too. You didn't try to get the IC out already did you? That might be enough to damage it, but just soldering caps around it probably wouldn't unless you had the soldering iron on the board a very long time. I always dread removing ICs, but at least you don't have lead-free solder to deal with on these older boards.

[Leizhg]

Reporting back after a long delay. Finally received the ceramic cap yesterday, replaced the existing one and still no success. So I resorted to replacing IC3. Woohoo, it worked!

Thanks everyone for the advice along the way! Very happy about the result and a satisfying journey.

Here is the video if anyone is interested:

https://photos.app.goo.gl/d4YwnTdkob7uRYwU6

Thanks again!

[Pixel]

That is awesome. You did a great job. You should go out and find some matching gear and save that too!

[Leizhg]

Thanks Pixel ! My next (under going actually) project is to restore a Sony TC-50. Don't have too high hope but let's see!

[Pixel]

Document your progress and let us know how it goes with the TC-50. I'll just say that if you use rubber rejuvenator liquid you should be prepared to let the thing air out for a few days outside because that stuff is awful.