Unfortunately this is one of those things which many of us could sort out in minutes if we had it in front of us but is nearly impossible to sort out remotely. You need to find someone local who knows about these things.
Well, I am not going to pay to have them repaired since they are university property, but the university would rather throw them out than have them repaired. I got them from university surplus since they won't buy more. I will spend a couple dollars on parts, though, since I can get that from the department's petty cash. I don't understand why I can't remove the PCBs completely and just wire the motor to a variable speed switch. Is this possible? I see homemade mixers doing this same thing with computer fans. I understand I have to convert the AC to DC, but surely there must be a simple solution rather than tracking down all the broken pieces.