Model A1174 with 2 GHz Core Duo or Model A1207 with 2.16 or 2.33 GHz Core 2 Duo

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Power cuts out after 2-3 hours

The iMac boots fine, works well but after 2 or 3 hours will suddenly completely cut out, as if the plug has been pulled out.

If you try to restart it’s dead.

If the unit is unplugged and left for about 15 minutes, replugging and booting works fine.

The plug and cable are seated well, I’ve done a SMU reset, and a PRAM. Apple Hardware test was clean, no joy

I’m guessing this is a faulty power supply, is there any thing else this could be caused by?

Answer this question I have this problem too

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I know this is an old issue however it would be nice to see a comment stating the final resolution

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Faulty Power Supply sounds like the case. It could be overheating, does it get hot?

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The problem was resolved by changing the power supply. I followed the ifixit guide for a 17" machine, mine was a 20" iMac.

Basic fixings were the same but in slightly different places.

The main difficulty was the main snap on connector for the power supply(black one) was routed under the chassis and I couldn’t get to the connector. Cutting the black wire from the faulty Power supply close to the PS as possible, made it possible, with tweezers, to re route the wire, under where the hard drive would be replaced, there was enough space under there, and it hasn’t caused any problem.

All works well.

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it would be great if you accept an answer (even if it's your own answer) - that way it is a resolved problem and others might find it easier to get their problems fixed

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+1 Jeremy for posting your resolution. Thanks

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It’s very cool at the moment but it has in sleep mode since start up a hour ago, I’ll exercise it and see if it gets unduly hot before cutting out.

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Good idea, it will be hot around the fan strip at the top behind the display.

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Hi

Didn’t feel wildly hot, last night when the machine switched off after watchindg a DVD for a couple of hours, so I did a test this morning taking measurements using the iStat widget.

I was running a DVD to keep the processor busy, hence the optical drive temp rise. final temp was after an hour, machine shut down after 1hr 10 minutes.

Temperatures are celcius, start up temp first, and last recorded before machine shutdown. Figures in brakets ar similar temps from 27" imac for reference if that helps

HD: 22-40 (39)

CPU: 26-40 (34)

Ambient: 18-22 (19)

GPU diode: 29-49 (41)

HD bay: 20-37 (40)

Mem controller: 23-43 (46)

Optical drive: 20-39 (40)

“No climategate fudging of figures here”

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Doesn't seem to be getting overally hot.

I haven't worked on many of the intel iMacs dont seem to have come through the workshop yet.

But could be a faulty supply, does the videgraphics cut out or does the computer just shut down? Could be a faulty temperature sensor maybe?

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Sounds pretty dead when the image goes, (No fan noise), degfinitely no sleep mode light.

Do I need to open it up and check those logic board LEDS?

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Jeremy will be eternally grateful.
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