After being preempted by an automotive repair last weekend, I finally got to get into the belt job on this deck. The kit I was provided was unfortunately not great. A couple of the square belts were way too small to work in any position. In the end I ended up using only the flat belt for now, as the others seemed to be in usable shape for the time being.
The replacement flat belt was a bit tight I think. Playback was quite slow. I had to crack the factory seal on the motor speed adjuster and turn it up some. This makes sense to me. More tension equals more friction and so more drag. Since this seems to be the first servicing of the deck belts, I thought it would be closer to correct at the factory setting. I guess as soon as you touch anything in these, all bets are off as they say.
Anyway, I wrote to the seller, he asked for measurements and has sent me out replacement belts. So we'll see if he has a flat belt closer to the one I removed, only not all stretched out. Fwiw the flat belt in the kit was said to be 86mm, was actually around 90mm and the one I removed was about 97mm (folder lengths), although it doesn't stay on the crown pulley so it must be somewhat stretched. I don't know how granular the sizing is, but I'm hoping I get something like 95mm. For now the flat belt I got is doing the trick. The unit plays not bad. I think the extra tension is causing a bit of flutter but it isn't too noticeable.
I haven't made a proper test tape yet. I do have a very good ear for measurement. The compare a factory album on tape to the same track on YT method works very well. Before long, I was flipping back and forth from an album on tape to the same album on CD fed into the line in. Very effective. I'm considering drilling a small tape speed adjustment hole in the back panel of the unit today. Some machines have this, some don't. I see no reason not to have one on this thing, especially if new belts might relax over time. I did use a plastic tweaker, although the adjustment screw on this motor is quite safe with no exposed components.
Finally, I'm having a good bit of trouble with the function switch but only in the Tape position. It's getting better, but I'm having to play with it a lot to keep the left channel coming through at proper level. I don't know if the switch is worn out in that position or if I'm just not getting the contact cleaner where it needs to go. (I've soaked it good a few times now.) If I can't get it working well, I may try swapping it with the Tape Select switch which is the only other switch of the same type. The Phono/Line In switch was doing similar things in Phono/Line In mode but that one cleaned up fine and works fine now.
So just fiddling with these old switches and a bit more cleaning and polishing while I wait for more belts. Happy Saturday all.