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mattbrewster

macrumors newbie
Original poster
Aug 6, 2009
10
0
Hi all,

I have an early Intel iMac (Core Duo 20") that of late is experiencing problems...

When I'm using it, it randomly shuts down and refuses to power on until a few minutes have passed.

When it crashes/shuts down I disconnect all cables for a few minutes, and then try to power up. Sometimes it works straight away, other times I need to try again in a few more minutes.

When I say "shuts down" I mean the power just goes, no screen, no LED, no noise, everything just dies. When I say "won't power on" I mean I press the power button but nothing happens, no screen, no beeps, no chime, no whirring, nothing.

Any ideas about what to check first? I personally think it's either (a) overheating or (b) the power supply is knackered or (c) both of the above!

I've tried a different power cable and also disconnecting all peripherals, no difference.

Thanks
Matt
 

ArcspacE

macrumors member
Jul 31, 2009
56
0
Could be heat.
How old is your imac?
Check out the 'HDDs failing' thread below.
 

jmulls

macrumors newbie
Feb 15, 2004
13
0
New Jersey
Same here

Same thing happens here, but it restarts. I suspect it is a heat issue since it happens on summer days when we do not have AC on in the house. Annoying.
 

mattbrewster

macrumors newbie
Original poster
Aug 6, 2009
10
0
It's an early 2006 iMac Core Duo 20" 250GB.

i'll install iStat tonight and post back my results.
 

mattbrewster

macrumors newbie
Original poster
Aug 6, 2009
10
0
OK I've installed iStat and have been using the machine for a while now. Temperatures are:
  • Local disk: 29
  • CPU: 36
  • Ambient: 26
  • GPU diode: 45
  • HD bay: 34
  • Mem controller 38
  • Optical drive 28
Do these look acceptable or are any a problem?

Thanks
Matt
 

indg

macrumors 6502
Feb 7, 2007
459
12
it's not that the gpu temp is high, but due to a flaw in the logic board, the system thinks it's overheating and shuts down. a lot of 2006 intel imacs have this problem, yet apple refuses to acknowledge it. it affects imacs with both Nvidia and ATI GPUs.

see my reply in another thread:
https://forums.macrumors.com/posts/8256017/

running the apple hardware test will not detect any problems because from the system's point of view, everything is running normally as it should be.
 

mattbrewster

macrumors newbie
Original poster
Aug 6, 2009
10
0
I've already tried resetting the SMC (i.e. unplugging it for 15 seconds), no dice.

Does the effectively mean that my £1200 iMac is essentially now an Apple-badged paperweight? Anyone know how much this will cost to fix, or if it's even fixable..?
 

killerrobot

macrumors 68020
Jun 7, 2007
2,239
3
127.0.0.1
If the SMC isn't resetting it, and it isn't always repowering right after that then it seems like you need to take in for a diagnosis. Your temps are fine - the shut off should be around 95C.
If it's the logic board, you'd be better of buying a new iMac, if it's the power supply it should be much cheaper to fix that.
Sorry.:(
 

mattbrewster

macrumors newbie
Original poster
Aug 6, 2009
10
0
Thanks for the reply. I'll phone up my local apple shop and book it in for a diagnosis, and my wallet and I will wait patiently for the result...
 

MattMoB

macrumors newbie
Mar 15, 2008
2
0
Hi Matt, did you ever come to a conclusion on this? i've got the same problem with my 2006 iMac, Just turns itself off.
I took it into a genius bar just outside London and they flat out refused to help me(wouldn't even attempt to switch it on) as it's a vintage machine. Slightly disappointed with the service i have to say.
Back to the point though, doing a bit of googling this seems to have been a common fault but i've found no reason or fix so far.
Any help is greatly appreciated!!!
 
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