Diagnosing a non-working Mac Performa 476?

From: Chris <mythtech_at_mac.com>
Date: Sun Jun 2 13:18:42 2002

>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.

Your start up bong should be a single smooth tone. If it is a "melody" of
any kind, it is not a startup bong, but rather chimes of doom. The melody
will tell you what may be the problem.

The first thing is to check the PRAM battery. Many Macs will not start
properly with a dead battery. If it is dead, Radio Shack stocks all 3
kinds used in Macs (but ironically, standard PC CMOS batteries are
special order). I don't recall if the Performa 47x used the square 4.5
volt, or the 1/2 AA 3.6 volt. I think it might be the 1/2 AA, but either
way, it will be pretty obvious when looking at the logic board.

Also, press the CUDA button on the logic board (again, I don't recall off
the top of my head if the 47x has one, but I think it does). This will be
a small red button on the logic board. I seem to recall on the 47x it was
either near the ports on the back of the board, or near the front by the
floppy and HD connections. But again, it might not be there at all.

The CUDA button will do a deep hardware reset, this will clear any
screwed up hardware settings it might have (and is usually recommended to
do after changing PRAM batteries, or adding or removing cards).

Finally, if none of that works, disconnect the HD and floppy. You should
get at the very least when no drives are connected, a grey screen with a
disk with flashing question mark.

If THAT doesn't work... do you have access to another Mac? Can you make a
known good bootable floppy disk? (you can download a 7.5 disk tools image
from Apple's web site). Build a disk, and put it in the drive
(reconnected drive that is), and try to boot from it. If your system is
working, but the monitor is dead, you will head the Mac doing a bunch of
accessing of the floppy drive as it boots (They will boot fine with no
monitor attached).


But with all this, I suspect the problem will be a bad PRAM battery, or a
need to press the CUDA button.

-chris
<http://www.mythtech.net>
Received on Sun Jun 02 2002 - 13:18:42 BST

This archive was generated by hypermail 2.3.0 : Fri Oct 10 2014 - 23:35:04 BST