Left channel in and out.

Hi everyone. I'm new so bear with me. I have a C-100f that I got from a freind that was in pretty good shape other than being old and dirty. I have gone through the whole thing and it works tip-top (almost). The problem is that my left channel is unreliable. I have cleaned all the switches and pots and the problem persists. I have it plugged in now and it's working great. I find that once I get the left channel going, it stays as long as I don't power it down with the power switch, so I just unplug it. Is this a common problem? Any remedy ideas?

Im no tech expert, far from it, but it does sound like a bad contact/ switch issue.
You could try plugging in some earphones and see if the problems the same through them?

I came across this same topic from another member a couple of days ago whose symptoms were identical. I beleive his/her culprit was the power switch, but I can't find the topic anymore. Am I onto something? Oh, and the problem is duplicated through the phones jack.

Found it! Turns out it was just a loose pin connector (marked "CN206"). Unplugged it, cleaned it, plugged it back in. Works like new now. Yeah, I fly by the seat of my pants.