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Re: Problem with Apple imac Power Supply
The most common problem with imac G4/800's are failing logic-boards. This will cause the mac to not power up at all giving the impression that the PSU is broken.
If however, you are indeed certain that the fault is with the power supply, they are available from many stores online
Power Supply for iMac G4 15" LCD (700 & 800 Mhz) 661-3184 614-0147
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Don't worry, I am a factory trained Apple expert! When you press the power button, do you see the white LED power light on the front of the iMac light up? Does it make ANY sound? If it is completely non-responsive, it will at the very least need a new Power Supply with the worst case being a logic board.
Checking the power supply isn't the easiest thing to do, it involves pulling apart the entire machine.
You can try resetting the SMC, unplugging all power, hold the power button for 5 seconds, replace power, then attempt to turn on.
if it still won't turn on, and assuming you didn't get AppleCare or it is expired (past 3 years) it might be worth taking in to an Authorized Apple Repair Facility and see if they will check it out for free. If it is under warranty, most definitely take it in or call 1-800-APL-CARE
If neither of those are an option,
a tear down from iFixit for the 20" model, it is most likely very similar for your model as well
Hopefully that helps.
Are you sure the iMac is really shutting down or just turning off the backlight? The tell-tale sing would be to let the unit fully boot-up (wait 3 minutes) and the press the button the apple keyboard that ejects the CD-ROM. If the CD-ROM door opens, you iMac is running with disabled or broken backlight.
The inverter circuit on the iMac G4 is known to be weak.
There could be another problem, though. The iMac G4 is also known to have weak internal power supplies. Here's how you can tell:
Hold down the CMD OPT "O" and "F" keys at the same time while pressing the power button. This will tell the iMac that you want to boot into the Open Firmware shell, bypassing the Mac OS X startup. If this works, your power supply is good, the inverter is good and you have a problem with your Open Firmware boot string. To fix the boot string, Power on the unit while holding down the keys CMD-OPT-P-R to zap the parameter RAM (PRAM) and reset everything to defaults.
If you were not able to boot into the Open Firmware shell, your problem is either a failed power supply or a failed screen backlight.
The last possible culprit is your iMac could suffer from "Bulging Capacitor Syndrome", where a batch of iMac G4s, iMac G5s another electronics were fitted with a bad batch of capacitors. Eventually, the caps will rupture and cause irreparable damage to the logic board. Only way to verify this is to pull the unit apart and visually inspect. If you see little green or blue cylinders that seem to be bulging or oozing a thick oily goo, that's your problem. Only recourse is to shop around on eBay and look for a replacement logic board.
You need a Access card to open the Imac from the back side and then you have to open LCD and under the LCD you can see the power supply.U need special tools for that.Dont try by your own.take it to a service center
The power supply is part of the motherboard in the iMac G4, so it's hard to change it. The repair would certainly cost more than the price of your iMac.
You can try to take off the small battery, and reboot it to see if it changes.
To open the mac lay it down, screen on the table (on a t-shirt). Unscrew the four screws (they wont come out, so just unscrew them. Pull the screws and take off the silver plate. Then you'll have access to the inside.
Hello, Sorry to hear you are having troubles,
Is this a 17” iMac G5, if it is, and I think it is, unfortunately, this iMac model was generation 1 of the all in one flat screen design and it's a bit of a Lemon... The hard Drive overheats the video card and the power supply. With time, these 2 elements burn out.
What you have sounds like the power supply.
it's a $300 repair, but, it might not be a good investment for you, the new power supply won't last much more than the first one and your video chip won't last much longer....
Best put the money and put it towards a new machine.
Sorry bout that.