Weird (?) mixer problem. What's goin on in there??

[foetus66]

I have a Vestax 170A mixer that I dug out of storage -- I've had it for a while (got it as part of a package deal with a PA system) but never had a need to use it. I was testing it out today to make sure everything works when I noticed there was no sound from the RIGHT speaker. The balance is set in the middle, and turning it all the way to the right just turns down the music in the other speaker..

Further troubleshooting indicated:
It's not the input because I tried all three channels.
It's not the output because I get the exact same thing when I hook up the TAPE/REC OUT to the amp (instead of the MAIN OUT).
It's not the amp because I tried my room-mate's mixer and it works fine.

So I decided to open it up, and found something a little curious -- two spots where the circuits have been deliberately damaged with a knife or something:

sorry they're blurry.

Could this be sabotage? I have a hard time imagining any scenario where someone would want to do that to the mixer... but it does look kinda odd in there and seems like an awfully hasty solution if there was some last-minute design revision. Or maybe this kind of thing is common practice and I just never noticed it before. Who knows, maybe those scratches have nothing to do with the output problem..

And if so, anyone have any other ideas what the issue might be?

[Jazz P Bass]

That looks like a factory mod to me.
Surely it is not sabatoge.
The hint is the wires & components. They go somewhere else.
I had a Yamaha GS32 in , the pre boards had the ground busses cut & rerouted with wire.
Must suck when you get a bad layout & you have thousands of bad boards.

[foetus66]

OK yeah, that makes sense. I wonder why one of the stereo channels passes no sound then. I was looking for anything that looked messed up or burnt on the circuit board but that was all I could see. I'd hate to throw away such an otherwise nice mixer.