Thorens TD 125 MK II speed problems

Hi, I've got two Thorens TD 125 MK II's. The first, I have have had for years, with the original Thorens arm. I bought a second one on eBay with a SME arm. Then I moved to Thailand where electricity is 220/50. The SME table had been modified so that I couldn't change the fuse for 220, but it worked for a while with a step-down transformer before failing.

I started using the old table with the SME arm, but noticed that I could see speed variations. This despite a UPS and/or AVR.

I got various kinds of advice from all over, including cleaning everything, oiling the spindle, new belt and pulley, capacitor change and speed controller tweaking.

I got the help of a local technical wiz to do all of the above, but the old table would still not keep a steady speed over time. So, he got the eBay table working again, but is also varies in speed.

He's ready to try the capacitor change on this one, but other than that we don't know what to do.

I suspected that I might have electrical problems, but the UPS or AVR should correct for that.

I don't expect the table to start up to the correct speed, but I need it to stay where I set it long enough to correctly record a few records, which I'm archiving to FLAC (record once, listen many times).

What can I do to stabilize the speed at this point?

Thanks,
Gritingrooves