mystery of the comatose flatpanel...

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doug-doug the mighty's picture
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mystery of the comatose flatpanel...

Okay, here is the situation. My wife's 15" flatpanel iMac went comatose this afternoon. She put the machine to sleep, left the room, took a shower, came back later and the machine was dead. Clocks around the house indicate a power failure or big enough of a hiccough to cause the flashing "12:00"s, but the incident was less than ten minutes.

Machine is a 15" flatpanel iMac, 800MHz, (last ones made with the DVD-R SuperDrive in the 15" body). memory is at least 512MB, OS is 10.2.8. Software is up to date as of August. Machine is pretty vanilla otherwise - wife won't let me mess with it, so you can rest assured that this is not user-inflicted.

Machine is plugged into surge protector. Other electronic devices around house appear fine (no other computers were on/asleep, so I have no REAL comparison).

Have tried the following:
- mashing keys on keyboard
= no change, power light is on
- clicking mouse
= no change, power light is on
- holding in power button for anywhere up to 2 full minutes
= no change, power light is on
- unplugging, letting sit and replugging
= when plugged back, power light comes on, fan starts up, DVD makes normal noises, then nothing
- pressing Command+Option+O+F while the power is restored (acrobatics required!)
= when plugged back, power light comes on, fan starts up, DVD makes normal noises, then nothing
- unplugging and then replugging while holding in power button
= when plugged back, power light comes on, fan starts up, DVD makes normal noises, then nothing
- posting the issue on AF in hopes of a quick answer from someone who has a better idea.
= ?

Thanks for any help you can give.

--DDTM

moosemanmoo's picture
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Sounds like a RAM or CUDA pro

Sounds like a RAM or CUDA problem. I'm not sure where the FP iMAc's CUDA button is, but someone else should. And BTW, surge protectors are only good for one use, unless they are UPSes.

doug-doug the mighty's picture
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[quote]And BTW, surge protect

And BTW, surge protectors are only good for one use, unless they are UPSes.

True, but I question if I actually experienced a 'brown-out', something a surge protector cannot fend off as it is actually aan under-voltage. I expect I may need to crak the case for the CUDA, but know nothing about the inside of these and hope not to have to go this far...

--DDTM

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PMU Reset?

Hey Doug,

Sorry to hear about this iMac.

Much of the internal work on a FP iMac involves separating the two haves of the round base, which in turn requires reapplying thermal paste and re-securing each half to a certain tightness, in order to prevent overheating.

But one thing you can do without "separating the saucer section" is reset the Power Management Unit (PMU) on the logic board. The Apple Service Manual for this computer recommends a PMU reset as one of the first troubleshooting steps when the computer won't power on:

1. Disconnect AC cord.
2. Remover user access panel from bottom of computer.
3. Press PMU reset switch once on the bottom side of the logic board. DO NOT press the PMU switch a second time because it could crash the PMU chip.
4. Wait at least 10 seconds before connecting the AC cord and powering the computer on. If it does not power on, don't try the procedure again; something else is wrong.

PMU switch pic:

http://www.applefritter.com/node/view/4724

Good luck!

Matt

doug-doug the mighty's picture
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:D

Ubber-cool trick, mein fruend!

Worked like a charm and the pic helped. The wife sends thanks.

Most excellent indeed.

--DDTM

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