ATTENTION: We advise not using Sleep mode for an extended period of time on your iMac G5. It may overheat and take out your power supply and midplane.
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<br>iMac G5 power supply burning (#2): Mid-plane assembly, power supply at fault; replacement
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<br>Reported by MacFixIt.com wrote:
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<br>Yesterday we reported on an issue where specific components of the iMac G5 apparently overheat and -- in some instances -- melt or otherwise suffer physical damage. We&rsquo;ve since received dozens of corroborating reports. In many cases, the problem manifests within weeks after purchase of a new iMac G5.
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<br>Mid-plane assembly, power supply at fault 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.
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<br>In most cases, users whose machines are still under warranty or AppleCare are able to quickly obtain replacement parts that resolve the issue.
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<br>MacFixIt reader Russell Logan writes:
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<br>"About one month after I received mine back in November, I, too, got the "hot electrics" smell.  Figured it was the iMac (20", only option was additional memory) and shut it off.  Had to check something, got back on the next day, and in mid-keystroke, heard a "Pop!" and it died.  I had purchased AppleCare and got a case number from them and directed to my local CompUSA for repairs.  Depot repairman called to tell me that the symptoms said power supply to him even though it was working in the shop (typical story, what?).  Despite this he ordered a new power supply and repaired the machine.  Got it back in 10 days (it had to be ordered). No issues since."
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<br>Another typical case from Roy Rhodes:
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<br>"We recently bought two iMac G5s for our company, one 17" combo and one 20" loaded. The 17" has had no problems, but after updating the 20" to 10.3.8, I got a call a few hours later from the owner that the 20" started to smell like it was burning and he had to turn it off. It had stunk up the entire office area he was in. We took it into the Apple store and they ran a number of hardware tests but nothing showed up during the tests. He took it in the back and looked inside and found that the power supply needed to be replaced. They kept it for 10 days and wound up replacing the logic board in addition to the power supply. We&rsquo;ve had it back for a little over two weeks with no further issues so far. We felt very lucky that he was using the computer when it started overheating. It got very hot very quickly and appeared to be a potentially dangerous problem."
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<br>Extended Sleep, high processor activity triggers Perhaps the most consistent trigger for this issue is an extended sleep period. Many users put their iMac G5s to sleep, only to return a few hours later and notice the a burning smell.
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<br>MacFixIt reader Eric writes:
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<br>"I too experienced the iMac G5 power supply burning smell. I had left the computer sleeping for about 4 hours, and when I came home, there was a burning electrical smell throughout the house. Two days earlier I had read about people having problems with their iMac G5&rsquo;s power supplies burning up so I went straight to the computer first, and it was the source of the smell. The computer was still sleeping, and did wake up when prompted. I used it for a few minutes, to check the discussion thread again, and get a phone number for Applecare. Once I shut down, the iMac wouldn&rsquo;t start up again. The power light would flash for a second, then nothing. I took the back off the computer and didn&rsquo;t see any obvious charring, but the burning smell was coming from the power supply. Called Applecare, and they sent me to a local reseller, who actually had a power supply on hand, and got my computer back to me the next day. My iMac was only 92 days old, sure hope this new power supply lasts a little longer. Perhaps the extended Applecare warranty is in my future? By the way, I always use sleep instead of shutting down."
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<br>Another trigger appears to be high processor activity.
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<br>Michael Blair writes: I do mainly word processing, but the processor fan of my two-month old 17" iMac G5 would ramp up when I ripped CDs or converted 192 bit MP3s or AIFFs to ACC and MenuMeters indicated heavy processor use. Two weeks ago, my wife did some processor-heavy graphics stuff and the fan ramped up as usual. After an hour or so we began to smell burning insulation coming from the machine. I shut it down and the smell dissipated. The next morning, I turned it on and in a half an hour or so the smell was back. Then the machine made a strange noise a couple of times and died. I called Apple tech support and we walked through opening the computer up, checked that nothing else was burned, then plugged in the power to check the diagnostic LEDs. It started up as soon as we plugged it in a seemed to run quite happily, although the power supply got pretty hot to the touch after a few minutes. The LEDs did indicate anything amiss, but the tech agreed that the power supply was likely bad, so shipped me a new one. It arrived 6 days later (a dual voltage model, as opposed to the original 120 v model). I installed it and everything is working fine now. The processor fan still ramps up when the processor works hard, but doesn&rsquo;t seem quite as loud, although that may be my imagination; it was never all that loud to begin with."
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<br>Home mid-plane, power supply replacement In some cases, users are sent the mid-plane assembly for home installation. The process is fairly straightforward, and some pictures of the operation can be found here.
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<br>Douglas Weittenhiller writes:
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<br>"I, too, am experiencing the whirring, humming problem of the G5.  I initially recorded the problem with my refurbished 17" 1.6GHz iMac, sent it to Apple and after an hour on the phone documenting the problem they sent me a new mid-plane assembly.  The mid-plane is basically the iMac&rsquo;s motherboard and install takes around 30 minutes (very good instructions).  However, while the noise initially went away, it&rsquo;s now back.  It&rsquo;s directly related to the amount of strain on the processor.  I have a 12" PowerBook, so I&rsquo;m used to fan noise, but this is much more irritating simply because of the constant change in pitch.  Either have the fans run low/medium/fast or get rid of the whine."
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<br>As noted in Michael Blair&rsquo;s report above, users are also being sent power supplies for home installation.
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<br>In some cases, users must have both the power supply and mid-plane assembly replaced.
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<br>David Eding writes:
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<br>"We never shut (our iMac G5) down but instead rely on the sleep mode for power conservation. One evening in mid January we noticed an electrical smell (the smell was similar to bakelite plastic overheating) in the room where the computer was. We did not immediately locate the source. The iMac was sleeping, or so we assumed, at the time. The next morning we tried to wake the iMac and were unsuccessful. I noticed that the white power light on the lower front of the iMac was flashing every second...different from the normal pulsing that is present when the machine is sleeping. This new pattern was a simple on-off blinking every second, with no dimming-brightening effect. I brought it to the local Apple Store for service. They took about a week to fix it. They replaced the power supply and something called the mid-plane (the latter had to be Fed-Exed from Apple as it was not in stock). It has worked fine in month and a half since that time."
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<br>mehr gibts hier http://g5support.com und bei Apple hier http://discussions.info.apple.com/webx?14@119.eqYGa1QxRBc.0@.68a4aa56