Diagnosing a non-working Mac Performa 476?

From: Brian Chase <vaxzilla_at_jarai.org>
Date: Sat Jun 1 21:42:46 2002

I've acquired a non-working Mac Performa 476. Unfortunately, I don't
have any other Mac gear to help me with the diagnosis. I've the
Performa 476 itself, which may or may not be working; I've got two
Macintosh Color Displays (M1212) which may or may not be working, and
one spare Performa 475 motherboard purchased from eBay. It was
advertised as pulled from a working system--but I've no way to verify
this. The seller was a reputable one, so I'm inclined to believe it's a
good board. The 475 motherboard is identical to that of the 475. The
difference between the two models being that the 476 shipped with a
larger internal HD.

When I power up the system, with monitor attached, the internal cooling
fan spins up, the hard drive spins up (and sounds normal), and the
machine chimes what I seem to recall as being the regular start up sound
for this era of Mac. However, the display remains dark. If I power off
the Mac, leaving the monitor on, the monitor makes a light
static/crackle noise; it's the sort of sound I normally associate with a
monitor that's lost the video input signal. I've played with the
brightness and contrast controls without any success.

If I switch the other monitor, the behavior is the same. If I switch
from the orginal motherboard to the one I purchased on eBay, the
behavior is the same. It's possible both monitors are bad and/or both
motherboards are bad. I don't have a multimeter to verify that the
voltages coming out of the PS are correct. Nor do I know that the hard
drive is functional--but I'd assume that nothing needs to be loaded from
the HD in order to get the display to come up.

I'm a bit puzzled, and wondering if anyone here with insight on these
Macs and their displays can give me any additional pointers.

-brian.
Received on Sat Jun 01 2002 - 21:42:46 BST