# iMac G3 won't power on



## #1 Rhapsody (Jul 6, 2008)

I have an iMac G3 400MHz slot-loading model that sounds half of the startup chime then dies.  I bot a new PRAM battery but that didn't help.  This is a very imporant computer, please help.


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## nixgeek (Jul 6, 2008)

Have you zapped the PRAM or reset the PMU?  Also, try swapping out the RAM inside and see if it's just bad ram.


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## #1 Rhapsody (Jul 6, 2008)

How do you zap the PRAM?  Do you press the PMU with the computer plugged in or not?  I don't have any RAM to switch to besides the sticks already inside.  I don't think it's the RAM anyway.


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## nixgeek (Jul 6, 2008)

To zap the PRAM, you  have to hold down Command-Option-P-R when you hear the startup chime.  Hold it down for a few chimes and then let go.

To reset the PMU, you have to hit the button inside the Mac ONLY ONCE.  If you hold it down too long or push it continuously, you can damage the Mac.  Think of it as a choke control for the Mac (like there used to be for cars).


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## DeltaMac (Jul 6, 2008)

I can't let pass this mis-leading troubleshooting tip. Pressing the PMU reset button will NOT damage your Mac, and you cannot damage it by holding the button too long, or pressing it too many times.
It CAN crash the PMU chip. That means nothing more than the PMU chip will be locked up, and will not start.
It is then reset by removing the PMU battery (the backup battery on the logic board), making sure the power cord is also disconnected. Wait a few seconds, then reinsert the battery (making sure the polarity is correct). This might also be a good time to replace the battery with a new one. Press the PMU reset button (once only), and wait 10 seconds before connecting the power cord. Start up the iMac, and reset the time and date.


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## nixgeek (Jul 6, 2008)

I thought I had read somewhere that this would do that.  Sorry if it was misleading.

EDIT: After doing a Google search, it seems there's a misconception by many out there that it would damage the logic board and battery when in fact Apple just says that the PMU would stop responding as DeltaMac said.  I guess at least I'm not the only one that was in error.


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## DeltaMac (Jul 6, 2008)

nixgeek said:


> I thought I had read somewhere that this would do that.  Sorry if it was misleading.
> 
> EDIT: After doing a Google search, it seems there's a misconception by many out there that it would damage the logic board and battery when in fact Apple just says that the PMU would stop responding as DeltaMac said.  I guess at least I'm not the only one that was in error.



Well, you are partially correct. If the PMU locks up, the PMU battery can drain completely within a couple of days. But, no harm done to the logic board itself.


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## nixgeek (Jul 6, 2008)

DeltaMac said:


> Well, you are partially correct. If the PMU locks up, the PMU battery can drain completely within a couple of days. But, no harm done to the logic board itself.



Yeah, I did notice it being mentioned that the battery would possibly need replacing if that were to happen.  It would only set you back about 5 bucks or so, though, so yeah not too bad....just a little inconvenient.


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## #1 Rhapsody (Jul 7, 2008)

I tried to reset the PRAM and I pressed the PMU button to no avail.  I think my new battery is not getting charged.  I had the battery that I took out tested and it came up as .006V.  Also my computer doesn't chime, it clicks and the hard drive spins then shuts down.


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## DeltaMac (Jul 7, 2008)

For that model of iMac, the symptoms that you describe probably mean that the power supply is not able to turn on the video, or the video high-voltage is failing. Either way means that the P-A-V board probably needs replacing. (P-A-V is Power-Analog-Video, and is the board that supplies all the power for your logic board, and the display. If you can find a working used part, then have it replaced. Or, just move the hard drive that you have to a working iMac.


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## #1 Rhapsody (Jul 7, 2008)

I left the battery in while the computer was plugged in and it booted.  Thank you for all of your help.


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