Quicksilver psu buzzing

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Quicksilver psu buzzing

The power supply in my quicksilver G4 constantly emits a fairly loud buzzing noise even when the machine is off. Additionally, if the computer is disconnected from the mains when it is reconnected it won't start up. The power switch lights up, but there is no beep and as soon as I let go of the power button it switches off. If I leave it a bit longer and try again the booting chime will sound and then it shuts off after 5-10 seconds. If it is left plugged in for longer it starts up normally and appears to work perfectly. Has anyone experienced a similar phenomena with their machines previously? Does anyone know exactly what might be causing it? Presumable there is a problem with the PSU and it is gonna eventually fail. I have tried resetting the PMU and replacing the battery, but it makes no difference.

PowerMac G4, Mac OS X (10.4.9)

Posted on Apr 22, 2007 2:02 PM

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Answer 1

Apr 23, 2007 10:55 AM in response to paulshaw

Have you done any work on the CPU? When I swapped out my CPU with an upgrade, I didn't seat it properly and the system wouldn't boot.

You could also strip the machine down to the bare bones (1 HDD, 1 graphics card, no externally connected devices except keyboard, mouse and monitor). Take out all the RAM and try booting. Without RAM, the machine will make a long beep sound if it can't find RAM to bootstrap the system.

I also had to replace the PSU in my G4 about a year ago. The fan finally gave out on it. Yours might be producing the sound from the fan, but I'm not an expert on this piece of hardware.

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Answer 2

paulshaw Author

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Apr 23, 2007 3:27 PM in response to AppleGeek

I did remove and reseat the cpu in case that was the cause of the problem, but it made no difference. I also tried booting the machine without RAM, and provided it had been left plugged in for a while it would emit a long beep.

I don't think it is the fan as it buzzes when the machine and fan are off. I think I might have to replace the power supply if it gets worse.

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Answer 3

Apr 24, 2007 9:58 PM in response to paulshaw

That's very strange that you hear a buzzing sound while the system is powered off. Does the buzzing stop if you unplug the power cable?

You reseated the CPU and no change? I guess I'm still wondering if you did any tinkering with the CPU prior to your problem?

If the system board and CPU are functioning normally, then without RAM the system will beep very quickly to indicate it can't find any to bootstrap the OS with.

Try to recall any work done on the system (if any) prior to the total failure and let us know. Also, did your system exhibit other problems prior to this total failure? Even minor issues would be worth noting.

The reason I'm asking these questions is because getting a bit of history on the system could help sort out where to look for problems.

If nothing else, if the buzzing sound is coming from the PSU, that's not normal in any circumstances. So it might be worth pricing out replacements online. I think they can go as cheap as $175 @ dvwarehouse.com (depending on your exact hardware model. Not sure what the cost of oversea shipping would be though (I see you're in the UK 🙂

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Answer 4

paulshaw Author

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Apr 25, 2007 4:25 AM in response to AppleGeek

Thanks for your help.

The buzzing disappears if the power cable is unplugged. I acquired the system from my University. It wasn't in use by anyone and was just lying around and so I don't know much about its history. However, the CPU is definitely working as once the system has been left plugged in for a while it boots perfectly and is usable. Its only when the system is first plugged in that it won't startup.

One odd thing is that when the system is turned on the power button briefly flashes off before lighting up again and then booting.

I am becoming increasingly convinced that the problem lies with the PSU and that I am going to have to replace it if I want to use the system.

PowerMac G4 Mac OS X (10.4.9)

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