Vintage DD turntables. Are we living dangerously?

Yes, 120v 60hz 23W.

I used contact cleaner on each pot, moved them back and forth and set them back to where they were.
it did not take care of the problem.
the motor seems to speed up to top speed and then come down to almost a stop.
the digital display does not change because it seems that it’s taking an average.

There's simply no way the calibration survived that.  Barely nudging those pots drastically affects the circuit, and in the drive circuit they all interact.  The mechanically tolerance affects the setting, so aligning witness marks won't work.  Best rule of thumb on quartz/PLL DD circuits: don't touch the pots unless you can recalibrate yourself, or have it done. 

 Under the platter, you will find a rocker switch labeled “run” or “hold”. In the run mode the tachometer will display the RPM from zero to the set value. For example if you are set to 33.33, then the tachometer will read from 0 to 33.33 over and over again. This can be very distracting.  Maybe that’s what you are looking at. Check that switch under the platter. Set it to hold and you will see a static display of the RPM. At least you should see that. If you see anything else, that is an indicator of a problem. Also, I would point out, with all due respect, that cleaning the contacts is not tantamount to changing all the electrolytic capacitors. Without meaning to sound dour, the more you power up the unit without having identified the problem, the greater is the possibility that one of the hard to find ICs is suffering a fatal calamity. 

Question for all you vintage DD experts out there.
I have just acquired a Technics sl10 linear tracker which looks to be fully functional and in good shape.

My question is concerning the RCA out.
It looks like it has a built in phono amp as the little button next to the RCA outs says mm/mc.
Does this mean it cannot be used through a phono amp as there does not appear to be a bypass to this , just choice of mm or mc.
Thank you

I definitely made things worst for my self.
and probably added more to a repair bill for moving those pots.
I hear that calibration cost $1000 for this QL-10? and I’m guessing that doesn’t include redoing the caps??
i wanted to fix it since it was my uncles.
worst come to worst, can I get a ql7 platter and still use my plinth and arm?
Thanks everyone for the responses.