On Jun 26, 2010, at 3:16 PM, Elliott Price wrote:
I inherited a G5, 20 iMac. It had bulging capacitors, and upon power on, it
worked, but had spasmatic video artifacting. After replacing some, then all
the capacitors, the problem still persisted, although it was much better.
Then, I got hold of a spare power supply that was a working pull, and it
works almost perfectly; but the video artifacts show up occasionally while
booting when it's still on the grey Apple loading screen. While in Target
Disk Mode, the artifacting is HORRIBLE. Once it boots, however, it runs fine,
and ran for almost two days straight with no problems.
So my question is, does anyone know why this is still happening? Should we
try getting a new power supply?
I'm going to use it as it is, but it irks me to know that it could fail
anytime... hmm...
Any isights would be appreciated!
I also know it's not the RAM, HD or whatever. It's definitely related to
either the caps on the motherboard, or the power supply.
It's probably the quality of the resolder job. I've got a similar situation
with a 20-inch pre-ALS G5 iMac. I replaced the caps in both the power supply
and on the logic board. For a few days it ran OK, then started throwing random
kernel panics, triple beeps/flashes on startup, weird intermittent artifacts.
Then it ran OK for a couple of days, then started doing stuff again. I could
induce artifacts by simply gripping the case tightly, so that led me to remove
the logic board and double-check all my caps' solder joints. I found several
that showed just the slightest bit of movement on one or both legs when I
wiggled the can. So I resoldered those caps, and all was well for a couple of
months, then it started again. I suspected RAM (2 1 GB sticks), and determined
which stick worked in which slot. Then I resoldered.
This time I removed all the logic board caps, cleaned up as best I could, and
resoldered. My theory is that because I was using a different solder than the
original lead-free solder Apple used, the bond between solders wasn't good and
tended to loosen with heat/cool cycles as the iMac was used. The resoldering
seemed to work. I used the bejeebers out of that iMac for a week or so this
past March. Some days it ran as a jukebox; others I used it to watch DVD
movies. I ran endless ASD Open Firmware and OS loops. I ran Apple Hardware
Tests, AppleJack and Memtest until I couldn't stand the full-throttle fan noise
any more. I thrashed the hard drive with Drive Genius 3 tests. Verified the
PRAM battery was 3+ volts. Swapped out the optical drive with another
known-good one. Ran it with just the mouse and keyboard. Nada. Nary an artifact
or kernel panic or RAM beep/flash. I set it aside during April and May as my
workbench filled with a constant stream of Macs.
I brought it back to my workbench and plugged it in a week or so ago. It
immediately chimed (it's always chimed), then started with the three
beeps/flashes again. I removed the original suspect RAM stick and it booted and
ran flawlessly. I put both RAM sticks in an eMac and ran Memtest for a whole
night. Not a problem. Put them back in their original slots, and beep, beep,
beep. Rats. Removed the stick from the suspect slot, and it ran OK.
So don't feel like the Lone Ranger. It could be we've got one or more weak
solder joints lurking. It could be that the logic boards suffered some internal
damage before we replaced the caps. Or it could be -- and this is my current
thesis -- that PGE is sending voodoo signals to G5 iMacs, and only G5 iMacs,
in neighborhoods where Russian spies have been living undetected.
-- Jim Scott
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