Okay, so I was being grossly unclear, sorry about that. There is actually a lot of PWM in the control circuit (it is PLL-based, not at all old-fashioned
), although the final stage driving the driving itself is analog, you are perfectly correct on this. However the problem does sound like a problem of Q6/Q7 staying fully open when they shouldn't. This calls for a complete check of the waveforms as a first move.
regarding the power supply I wouldn't just try changing the electrolytics, even though recapping is a common reflex in overhauling these oldies. If you want to be safe, the solution would be to change not only the caps, but also the rectifiers and the regulators, which I've seen fail much more often than the caps, and usually in strange ways that are difficult to spot. I would do this before any other action, including the waveform check above.
I have never seen a case of excessive friction on a Revox TT motor so I cannot comment, but I suspect that such a problem would be easily spotted by spinning the unpowered motor by hand. It should rotate freely and without noise, otherwise you have a friction problem.
If all this fails, there is still the possibility to send the turntable to the Revox service centre in your country, they still service them (well, they do it at least in France and in Belgium).