Vintage Synth Repair

Hi 
I am looking for some help on a Proteus 2k.

All 5 knobs on the front read max(127) at a little past half way on DIAGNOSTICS 4 Panel Test.
Went to 3 Calibrate knobs and fixed them up, but after a power cycle they were back to the half way point.

I though it had flash in it. Is there a battery (can't see one with the top off the chassis) ?

The data wheel values jump back and forward if turned at even moderately fast. I have read that some contact cleaner like DeOxit will fix it. They suggest that you pull off the knob and spray down the shaft. Is this correct??

Finally it is missing the plastic power button. Anyone with a spare?

Thanks

Royce