[Coco] Broken CC3

[George Ramsower]

 Well, DARN!

 I can't figure it. I went through the switching power supply and can't find 
anything that's causing the noise and ripple. I've changed several suspect 
caps.

 The ripple from the head stepper in the disk drive is showing up on the 5V 
line. I've buffered the 5V line with a 2200uf cap to the coco and the 
problem persists. If I DIR 1, the coco will give an I/O error(there is no 
drive 1). If I DIR to the drive that it does have, the coco crashes.
 I tried another drive and the results were the same.
 If I don't put a disk in the drive, the motor won't spin. This results in 
head movement, but no motor, no crash on the coco.

BTW, I only use 3.5 inch drives and I'm doing all my tests in RSDOS with a 
Disto SCII. However, I did try with a Tandy controller and the results were 
the same..

 It's odd that if the drive's motor isn't spinning, the coco doesn't crash. 
I can still see the ripple from the head stepper on the 5V line to the coco.

I thought that perhaps when I typed DIR something was being introduced to 
the memory that might be causing the crash, so I did a DSKINI(0) and the 
coco crashes after only a few tracks.

I'm wondering if perhaps there may be a bad cap somewhere on the coco.

Ideas? Suggestions? I'm about to start looking for hair on my head to pull 
out. This is exasperating.

George