Diagnosing a non-working Mac Performa 476? - test-drb@ccmp.vtda.org

3 Jun 2002

...
  -----Original Message-----
 From: Brian Chase [mailto:vaxzilla@jarai.org] 
...
  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. 
Would you believe that the whole thing may be working? ;)

First thing to do would be re-initialize the "parameter RAM."  Hit
command-alt-p-r on power up.  (I have seen corrupted PR cause this
kind of problem.)  There are also a couple of things that you can
(very safely) reset with other hot-keys.  You'll have to look them 
up, though.

You might check to see if there's any flash or what not on the monitor
when the computer comes on.  If the monitor has a power-save mode, and
starts up that way, does it turn on at all?

... but now that I read the next paragraph :)  

...
  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 
Very strange.  What's common between the two boards?  Do you have, or 
can you get, a known-good monitor?

Are you using the same RAM in both boards?  That could be suspect.  If
you've been plugging the drives back into the board, don't.  Take
everything out -- including un-used cables -- except what's absolutely 
necessary.  Try again that way.

...
  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 
This is also a problem.  Just a stab in the dark, try blowing the board
out.  I've seen some strange dust-bunny related problems with macs. :)
Make sure there's no way the board can short itself out to ground
somewhere...

... and get a multimeter. 

...
  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. 
Nope, but again, take it out, and the floppy, and whatever else (boards,
etc) you can.  Bad hardware makes computers do funny things.

...
  I'm a bit puzzled, and wondering if anyone here
with insight on these
 Macs and their displays can give me any additional pointers. 
Err -- you could also get an adaptor to plug a vga monitor in, and use
a monitor you know works, to eliminate that possibility.

Chris

Christopher Smith, Perl Developer
Amdocs - Champaign, IL

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