Sony TA-1150 Only Mono

isidor3

Honorable
Mar 10, 2012
2
0
10,510
Hello,
I've been trying to repair an old sony TA-1150, The amplifier only outputs mono, regardless of what "mode" it is supposed to be in. (although if the switch is set to mono, the sound barely plays, only cuts in in a somewhat regular manner.) Also, if the input is connected to the power amp input, then stereo works perfectly, but then volume, input, and tone control do nothing (which I believe is the intended design)

I've taken it apart and looked at the switch, but there isn't anything visibly wrong with it, although a stripped screw is preventing me from removing the the switch completely. There is also no other burn marks, destroyed components, bulging capacitors, or cold solders that I have found.

I'm currently a full time college student, and we have a few electronics labs on campus, so I could try bringing it in and getting the switch completely out
but I guess the question is this:
is this likely a problem with the switch, which I could probably fix, or am I missing something else that could be causing this?

the service manual is available at here if anyone can tell anything from that.