[Adam]

Cleaned that switch, then the other channel came up, but only for a while - it kept going in and out.

Cleaned the head - a little better.

Then I noticed when it tried to change tracks that the mechanism that moved the head up and down was sticking. I got that to work and messed around with an adjustment for the head height. After this, it would play the first 2 tracks fine, but not 3 or 4.

I moved that head height adjustment enough for it to play track 3 when set to track 2, to prove it wasn't the tape.

Then, I noticed that there were only 2 positions the head was going in, that it didn't go up any further when switched to track 3 or 4, that it just went back and forth between the track 1 and 2 positions.

But then I thought since this plays quad tapes, it has to be able to read 4 tracks at once anyway, so it really only needs to have the head sit in two positions, and switch what part of the head it's using - and that's why there's that 2-4 channel switch on the front.

So now I think it's either that switch, or something to do with the rear channels (which are also used to play tracks 3 and 4), that is my next problem with this thing. But I went to bed before I tried anything else.