I'll order a replacement IC and let you know what happens in a week or two.
If it's not too late, I'd order a couple of them. After all, you do have
a second Lisa drive that needs repair (IIRC), and also it's possible
something in the motor -- like those capacitors I mentioned -- could be
damaging the chip. You check for such things of course, but it's always
possible you could miss one...
I am still curious about that 'extra' white wire...
-tony