Well, my old iMac G3 has finally stopped working. It will not power up at all. Totally no response...dead. Does this mean a broken power supply? Can I be sure that this is the cause? If not, how should I diagnose?
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2014, January 2 - 1:15am
#1
iMac G3 will not power on
Comments
2014, January 2 - 3:59am
#2
Oh no another one of those that goes toast! Slot loading or tray loading? Anyway before doing anything critical, it seems that a dead pram battery prevent some of those models to turn on. If it is not the pram battery, i would test if there is voltage in any of the pins in the what... 24 pin connector? from the power supply. The big one. With a multimeter,and the mac connected to the outlet of course, place the black tip on any of the black terminals with black cable, and the red tip on any other color. If zero volts come from any combination then it's probably the power supply. Probably some dead capacitor( s ). <-- sorry about the space a smiley appears there if no spaces
Also found this, quite interesting reading, but i am assuming you didn't have funny odors or smoke or artifacts in the screen before it died.
2014, January 2 - 6:11am
#3
Thanks for the tips, macjames. I will try that. BTW it is a slot loading one.
2014, January 2 - 7:59am
#4
I owned a slot loader iMac, I seem to recall it having trouble starting with a dead battery. But its as macjames says, so test the battery 1st, if its holding a charge less than 3 volts, replace it. If its the PSU thats dead it wouldn't surprise me either.
Check for leaky capacitor[s] <-- angle bracket[s] make a good substitute for parentheses here 
2014, January 2 - 8:42am
#5
By the way i didn't mention leaky capacitors because i have seen too many power supplies from the era (including G4's ranging from graphites to MDDs) and capacitors fail with no leakage. Unless a component looks blown or see a burned zone, it's too hard to find the culprit. You need to follow the traces until you see no voltage. That reminded me of something else... check for fuses.
By the way again, i was going to post a link that i found about other imac common power failures but i got the moderator thingie.
And last: Thanks for the brackets tip MTT
2014, January 3 - 12:45am
#6
Well, I unplugged and moved the iMac in preparation for opening it up. I then checked it again and, lo and behold, it started up. This is mysterious because I had already done the obvious and trivial check for a loose power cord before I posted here. Anyway, thanks to all for your suggestions. I have a feeling I will be needing them sometime soon.
2014, January 3 - 10:40am
#7
A nice new years present, a self healing iMac!
As vintage Mac expert, you certainly did image all your volumes and checked with TechTool Pro. 
2014, January 3 - 11:46am
#8
Yes, all imaged, awaiting the inevitable, whenever that will be. Yet to give it a check over though.
2014, January 3 - 12:39pm
#9
Yes, all imaged, awaiting the inevitable, whenever that will be.
We all do… *sigh*
2014, January 3 - 10:17pm
#10
My Mac Pro 4,1 power supply died (this is the only reason I could find for the strange behaviour and crashes). Back to original Core i5 Hackintosh again (sigh).