EDIT:
They're all repaired and functional, except the one with the exploded capacitors which cannot be helped by me.
My question is this: My repairs are pretty standard stuff, but I tweaked a few things that seemed to help. Would it be worthwhile for me to try and organize some specific information about such and post it here?
THIS CONCLUDES THE 'NEED HELP' PART. BELOW ARE THINGS I DID IN THE REPAIRS
Both of the model 2 systems that came in were dead from fuse problems, so I pulled the fuse (all of them were back-of-board square fuses instead of the top mounted ones) and replaced it with a wire-lead fuse holder sticking out the side. Once they powered on, one of them worked fine except for the occasional grinding, and the other, plus my original system, would not stop grinding the laser transport. I pulled the assemblies completely apart and completely de-soldered, re-shaped, and re-soldered the momentary-contact switches that tell the laser when to stop moving.I reassembled the units and took a 3M Command strip for poster hanging, cut small squares off, and placed 2 of them together on the side of the plastic housing of the switch which is the point of contact for the laser assembly. Then I cut a smaller square and attached it to the laser assembly's little bumper itself. I did this to all 3 systems, even the working one.
The first time I powered each of them on, they ground momentarily. But from then on, they have not ground much if at all and all three have played games and CDs from track 1 to the highest track with no problem.
The model 1s were an easy, easy fix. I'm kind of ashamed of the guy who was selling them. The first one was actually not borked at all. It played the minute I powered it on. The second one's ribbon cable was disconnected from the drive. The third one was a matter of changing out the drive belt and getting the thing pieced back together.