# Power Mac G5 Will Not Turn On



## flebbes (Jul 24, 2008)

I recently purchased a Power Mac G5 Dual 2GHz from ebay. I tested the computer a couple of weeks ago when I first got it, but wasn't able to actually set it up with all of my music gear until last night. I installed Logic Studio and a driver for my firewire audio interface and started downloading all of the updates. While downloading the updates the computer just turned off. I wasn't in the room, but when I came back in it was totally off. I tried to turn it back on by using the power button in the front and it won't turn on. It clicks once then clicks again a few seconds later, but no light and no power. Everything else that is plugged into the same power strip turns on. I reset the PMU, and even the graphics card just to make sure. I still get nothing. I have exhausted apples support page, and I don't know what else to do. Please let me know if you have any helpful ideas. Thank you, Andy


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## MClever (Jul 24, 2008)

First, disconnect all peripherals and retest.

Otherwise, see the voltage test points in this previous link
http://macosx.com/forums/hardware-peripherals/298426-how-test-g5-power-supply.html


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## Hughvane (Jul 24, 2008)

I note this post on another forum - good idea, spread the net. Reads to me like either
1. a power supply unit failure,
2. boot sector of hard drive corrupted or damaged,
3. internal hardware damage.

Check the PSU for any smell of cooked components. The clicking noise suggests a relay failure. Check the voltage setting (if applicable). You've checked the graphics card, what about the RAM seating, in fact any added card or item that is not motherboard native.


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## flebbes (Jul 24, 2008)

There is no smell of cooked components. With the audio interface I use, the speakers make a popping sound when the computer turns off and they are still on. I heard this from the other room and this is what alerted me. I checked all of the RAM and it is clipped in tightly. What do you mean by checking the voltage setting? I am also not familiar with a relay failure.


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## Hughvane (Jul 24, 2008)

Voltage setting (if applicable). Round the back of the G5, where the power cord plugs in the _may_ be a small slot through which you can see a sliding switch with voltage and current settings printed on it. If the computer was working okay for a while, then I doubt the voltage issue is the problem.
Relay failure - a relay does as its name suggests, it relays voltage to various other components within the PSU. The relay may be a simple diode, although they don't click, it may be an electromagnet. Do you have a multimeter, and do you know how to use one to test circuits and voltage output? If yes, and you can locate the correct terminals, then check on power *in* to the PSU (which seems to be okay from what you've reported), and then power *out*. If there's nothing, or fluctuating voltage out (could be from 5 to 12 V) then there is probably a PSU problem.
RAM seating - remove the sticks and then replace them, swapping them about. Remember to earth yourself to the metal chassis of the G5 first (I use a wrist strap) with the power cord still plugged in but power OFF.


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## crash_af (Jul 26, 2008)

Does the LED do anything when you press the power button? If it is coming on when you press the button, does it start flashing?

Later,
Joe


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