Rotel Turntable speed

I purchased a Rotel RP-2500 turntable used and it won't keep a constant speed. I've searched the web and tried all the suggestions I could find. New belt, cleaned pots, greased spindle, and replaced (what I assume to be) the DC filter capacitor. The fluctuation in speed seems to follow a pattern (if that makes sense) - as if it slows down and speeds up at the same platter orientations each revolution. Could the platter be bent? I don't know if it's an electrical or mechanical problem at this point. Any clue if that motor can be substituted? Any other suggestions before I get rid of it? It's a good table otherwise...

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I've read before not to use petroleum based lubricants with turntables, especially those with dust covers. Over time, the petroleum vapors degrade rubber mats, stylus suspensions and rubber belts causing them to dry out, become brittle and crack. The vapors become concentrated while trapped inside a dust cover. It happened to me ruining a mat and doing god knows what to my stylus's suspension, which of course affected it's compliance. I didn't care about the belt, it was cheap.
Peterman1983-Motors can develop dead spots. If I wanted to test that theory, I would put an ammeter in circuit and see if the current draw was constant or bouncing. However, if that's the case, there should be more "dead spots" along the platter's revolution for each dead spot of the motor's revolution. Think of a 10 speed bike in low gear, many pedal rotations to get one wheel rotation.
If you want to check the balance of the platter, support it vertically, the heavy side will always reveal itself. (Lawnmower blade balance method).
I'm not sure how your turntable regulates it's speed, but the electrolytic capacitors in my HK T60 failed causing it to run overall slow, with much wow and flutter. The unit seemed to misbehave more on the outer tracks, I'm sure you can guess why. Replacing the power supply caps did nothing to fix the situation, the problem was in the motor driver circuit.
Before I'd start tearing things up, I'd verify the belt is the correct size. Too tight and it pulls the platter over, too loose and it falls off. Also, clean all surfaces the belt contacts, as well as the belt itself. In addition, you should make sure the platter is level and at the correct height, if at all possible. If there is bad spot on the main bearing, when you disconnect the belt and spin the platter, it should always stop at the same spot where the drag is greatest.

Thanks to both of your for your responses. I'm confident in the belt size, but I will try your method of letting the platter spin freely, to see if it stops in the same spot each time. There are some caps in the motor control circuit which I did not replace. That may be my next step. Again, thanks for the tips... very helpful.
Hi Peterman -- My Rotel TT from the 1970s has developed the same issue -- a wavering speed that's particularly noticeable with symphonic material. Did you ever sort this one out?