A service manual won't really tell you how to change belts or pinch roller but it should give you a good idea what needs to be disassembled (and in what order). It's good to have for that reason. It, of course, will also tell you how to do a more involved service, align etc... but you shouldn't worry about it. You first order of business should be to get the recorder up and running as fast and as cheap as possible. If it sounds and works good then it's good.
The first thing you need to do is actually play back and record some tape to check functionality. When doing so, note any issues etc.... You definitely want to check if the rubber pinch roller is on the hard side (not going sticky) and if so, how dirty it is, maybe looks like it has brow oxide residue. You want to clean that off using some isopropyl alcohol (at least 90%), until all you see is some black. In the (near) future you may want to invest in some rubber conditioner (
MG chemicals rubber renue is best). Just a once over is enough for at least a year. You don't want to do that often as this is done merely for restoring the natural grip of the rubber (but only if the rubber roller is hard not soft, on the gooey side - otherwise it needs changing). For routine cleaning, when it gets dirty again, you can just use some warm water and q-tip or small lint free rag.
You also NEED to clean the heads (in the direction of the tracks) with at least 90% isopropy alcohol and q-tips. This should be done every several hours or thereabout of actual tape to head contact. See if there is a "ring" of oxide on the spinning capstan shaft. This should be carefully cleaned too. Be careful that no cotton gets tangled into the capstan shaft base.
The belts probably will need changing if anything is dragging or you get audio problems (wow and flutter), speed issues etc.... Belts stretch overtime or disintegrate. I see eBay sellers selling belts but many are too damn expensive. Those belts shouldn't cost more than a few bucks. If the belts are gone, I would very carefully remove them, measure them and buy ones just a bit shorter or you can get ones selected for you by some seller (but it will be more expensive). You may wanna send the measurements to this guy and he may have the ones you need:
Vintage Cassette Deck Belt KITS and instructions.
Haven't done business with him but he's worth the try.
Another you may wanna try is this one:
Audio Cassette Parts
Lots of belts etc......
Any name brand chrome tape (type II) or standard tape (type I) will work fine. The quality of those early recorders is usually so good that you can get superb audio from just about any kind of tape.
The above recommended minor servicing is really needed on recorders of this age and should be viewed as normal.
If you get a chance, post a photo of yours.
