Sony TTS-3000 servo speed issue...

Hello all. Looking for a hand on this guy here.

I recapped the servo unit and it worked fine for a few hours until I put it away in the garage. Fast forward about 6mo or so when I decided to dig it out and give a listen.

Speed is uncontrolled at this point. The ground leg of the motor circuit isn't getting any servo action as far as I can tell. I see a varistor in there next to the freq generator input and am assuming that is the heart of this servo control. The freq is fed to a gain stage (transistor) and on to the varistor so as to vary resistance to ground. Higher V (freq) equals more resistance, which in turn slows the platter.

That's how I'm deciphering the circuit, in it's most basic form anyhow. And that's where I'm lost. Anyone take a look at the schematic and give me a possible lead here? Thanks much.

Sony TTS-3000 Manual - Professional Turntable Motor Unit - Vinyl Engine