It's a neat looking design. Joe you're a braver man than me for even trying to fix a computerized machine. That's something I don't even want to attempt. It's also a good example of why I don't like computerized machines in general. There's too much that can go wrong, you have to replace modules instead of individual parts and parts are quickly made obsolete and no longer available.
The Riccar I picked up the other day is about as advanced as I want to get. As far as I know it's just basic electronics, no computer to worry about. It has 3 push button speeds with "needle up" and "needle down" stop buttons. It looks to me like the "needle up" and 'needle down" positions are controlled by 2 sensors at the end of the hook drive shaft. After I replace the gear and get it running if I (or my daughter Olivia) don't like the push buttons I'll look for a way to neatly install a bypass switch and a foot pedal controller. (I think this should have been done at the factory and I think the parts are available to do a clean job). Right now I would rather lift my foot to stop the machine than reach for a button.
Rodney