Kurzweil PC88 Power Problem

I have a Kurzweil PC88 that I’ve been struggling with. I replaced all the rubber contact pads and it plays wonderfully… for a few minutes then something happens with the power and the unit goes through the startup cycle. This did happen prior to the pad replacement and only happens when played. I can run demo mode indefinitely and it doesn’t cut out.
I resoldered the big cap on the power board since it was a bit lose but nothing else seems off.
Any ideas?

This could be a voltage regulator problem. If you can try and run the keyboard with the case open and look for anything getting really hot or before the power cycle happens. Or any heatsink not properly connected also.

Regards Darren