Drive Belts are done, practically erode into goo (really nasty tary gunk).
Amazon sells the replacements, you'll need 2, for about $12 per pair: Part X001PK6EIR
The surgery is in depth, complete disassembly of the unit required, a few dozen P2(regular philips) screws, about 2 hours. Acetone (nail-polish remover) for old belts removal/discard and cleaning of drive pulleys.
Aptitude Req'd: 5 of 10 (attention to disassembly essential, then reverse order)
Sadly in my case the CD reader was also deteriorated (skipping, dodging tracks) so restoring the turntable's motion/function was not the whole of the repair. Since the above required demounting the laser-side of the reader it's likely a better economy to address it's replacement in due process.
It's no wonder, though, that SONY no longer mfgs these units, as nifty as they are.
Good Luck!