22 May
2012
22 May
'12
12:06 p.m.
I have a model 4 that developed a problem with the video / floppy
drives. When both floppies are plugged in, no video.
With one floppy drive installed, the system works OK. I remember the
flex cable was usually the culprit.
I've inspected the cable and it looks ok, should I be looking at
something else?
THe flex cable (the one from the CPU board to the floppy controller
board) is a common cause of problems with the M3 and M4, but I don;t see
how it could cause the machine to work with 1 drive and fail with 2. It
carries part of the CPU bus, the floppy controlelr board works out how to
select drives.
I would suspec that for some odd reason the PSU (the one for the drives,
on the side of the drive tower) is shutting down when you add the second
drive. Either that drive is defective (and drawing too much current --
does it matte which derive is conencted if you only have one of them)? or
that the PSU is defecitve nad can't supply enough current to powe the
controlelr and 2 drives.
-tony