More on iMac G5 power supply burnout: Bad capacitors seem to be at fault

We've continue to cover a number issues with iMac G5s apparently overheating, and generating excessive fan noise in an apparent effort to cope with the heat. In some cases, the overheating can cause actual component damage, causing the power supply and other parts to fail.

As noted yesterday, users experiencing these problems generally must replace one of two hardware components: the power supply, or the "mid-plane" assembly which consists of the motherboard and other circuitry. In most cases, users whose machines are still under warranty or AppleCare are able to quickly obtain replacement parts that resolve the issue.

Yesterday we also reported that this problem afflicts more first generation (rev A) iMac G5s than later (rev B, or Ambient Light Sensor) models. The later, less susceptible models include the iMac G5 20" running at 2 GHz and other models sold from June 2005 onward.

We've now received additional confirmation from Apple resellers and authorized service providers indicating that the earlier (revision A) models are indeed more susceptible to this issue.

One reader, who wishes to remain anonymous, cites bad capacitors as the reason for failure. He writes:

"Anyway, 90% of issues with the iMac G5's are because they used some cheap capacitors, that tend to blow really easy.

"The company that made the capacitors, no longer exists. The issue has been resolved on the newer units. If you have a first generation iMac G5 , you have the cheap capacitors, and there is even a hint of trouble, I'd recommend getting it fixed.

"Again, please pass this info on as anonymous, I'd get in a bit of trouble if I was passing internal info."

Feedback? Late-breakers@macfixit.com.

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