Like Old Steve, this sounds to me like something you'd have a real problem doing.
What follows is my advice if you really intend to scrap the unit:
First, take a good look at your sprocket gears (the ones with the teeth), if any one of them is worn-down or chipped-off, that would explain your symptom. Make darned sure there aren't any foreign objects stuck in the moving parts
that would gum-up the works.
1) Convince yourself that you're going to trash the recorder. That way if you try to fix it, you won't feel bad if something goes terribly wrong in disassembly or reassembly.
2) If you don't have the operator manual that came with the deck (sometimes they have mechanical exploded views of the innards), Google a free service manual, or schematics on your make and model. What you're looking for is an exploded diagram of the mechanical assembly, and/or instructions about replacing the belts.
3) Find the replacement belt kit for your recorder, and if it isn't too expensive, buy it.
4)Make sure the deck isn't plugged into power. Look at the assembly carefully, and determine which chassis screws are holding the assembly in place that prevents you from getting to the rubber belts. Carefully remove the
assembly blocking access to the belts, being sure you know how to reinstall it when the belts have been replaced. This is a delicate operation because everything has to be reinstalled exactly the same way you originally find it.
5) If you do all of the above and it doesn't fix the problem, a service guy would be needed.
I'm suggesting all this trouble because the vast majority of belt-driven recorders I've worked on are belt issues. The belts get so worn they slip; or stick, if the rubber deteriorates.
I'm only suggesting this because you said you'd probably have to trash the recorder. All the previous advice from guys on this site are valid. The recorder should be looked at by somebody who knows how to work on them.