iMac 8.1 early 2008, overheating at the PSU board area

[d3v]

Hi all. I have this iMac here that is overheating after about an hour of use and subsequently shutting itself down because of it.

I've stripped everything down and checked all three fans and confirmed they are spinning. The power supply board on the upper left corner (if viewing from the rear) is particularly hot so I'm wondering if there's a good chance it is faulty and a straight replacement would solve the issue?

I've tried fan control software and I think it helped, but not enough, it just delayed the inevitable overheating/reboot loops.

 

[JustInspired]

Is the cooling system clean, fins unclogged etc?
Thermal paste/pads - good?

 

[d3v]

Hi, yeah surprisingly all fans and vents were free of dust, didn't check the thermal paste, though.

 

[anonymous Mac Tech]

Hi, yeah surprisingly all fans and vents were free of dust, didn't check the thermal paste, though.

There is not really any thermal paste to check on those. Power supplies don't unsually "overheat" in those machines. May want to pull it and check for burn marks on it and on the inside of the enclosure where it mounts. Download and install istat pro (its a dashboard widget). It's very good for monitoring fan speeds, temps, and a variety other things. After you have that installed, run many instances of chess and grapher to ramp up the processor usage and build up some heat. Then you can see the temps and if the fans ramp up with the heat.

Other than that I'd recommend the usual things like SMC and PRAM resets.

My gut would tell me it's more than likely the video card on its way out.

 

[d3v]

There is not really any thermal paste to check on those. Power supplies don't unsually "overheat" in those machines. May want to pull it and check for burn marks on it and on the inside of the enclosure where it mounts. Download and install istat pro (its a dashboard widget). It's very good for monitoring fan speeds, temps, and a variety other things. After you have that installed, run many instances of chess and grapher to ramp up the processor usage and build up some heat. Then you can see the temps and if the fans ramp up with the heat.

Other than that I'd recommend the usual things like SMC and PRAM resets.

My gut would tell me it's more than likely the video card on its way out.

Excellent thanks for the tip on that monitoring software. Will get it running in the imac asap and let you know.

I did pull the power supply board out and there is no burn marks or bulging caps, however it is definitely the power board that is generating the heat, unless it's the hot air being blown up from the fan below it, but I doubt it.

With it being an AMD graphics chip you might be right I did notice a copy of football manager 2012 installed on the mac so god knows how much stressful 3d gaming has been done on this poor thing.

 

[d3v]

Ok iSatPro is reporting the power board at 60 celcius at idle, which must be abnormal? All other temps including the GPU are normal in my experience.