Here's a large photo of what I did, just in case I didn't do what you had suggested...

http://www.retards.org/projects/tmp/DSC_0010.JPG

I looked at the schematic for the analog board from your "Classic Mac Tech Info" document, but didn't see anything. I didn't expect to.

I don't understand why/how a spike would cause it to try and read the disk over and over. The rebooting makes sense.

One last bit of info... if I turn on the mac with the switch open (L1 and C2 not connected) there's no chime, and the disk-drive immediately just starts ka-chunking away.

Also, I double checked the mods with a continuity tester.