G5 Won't Power Up - Light Stays On

Hi all,

My daughter has an older G5 desktop and was running I believe Snow Leopard on it. Everything seemed to have been working for months.

Was going to replace the monitor and had her shut down. Didn't have a correct plug for the new monitor so rehooked the old one back up. Tried to turn on machine and nothing.

The light stays on (not sure if it ever went off as I just unplugged the monitor when the screen went dark) but nothing happens. I tried holding in the power button to manually turn off (or on) the puter but it does no good. Tried unplugging the machine for a while but still no joy. When plugged back in the power light comes on and stays but does not boot up or turn on any of the fans.

I took off the covers and looked inside. Nothing smells hot or fried. The fans won't engage. There is no power to the keyboard or monitor. I looked for a fuse but didn't see anything inside other than a PMU? reset switch which I pushed but still nothing.

No chimes, no sad Mac just nothing.

This leaves me with three possibilities that I can think of...

1. The power switch is bad

2. The power supply has either blown a fuse or just went out.

3. The motherboard has problems

Anyone else out there have anything similar happen or can give me a suggestion (BESIDES buy a new machine - very limited budget) on what to test before I start ripping out components?

Thanks in advance for your help,

Clark

Well if it is a G5 it can't run Snow Leopard as that is Intel only.

I would think your diagnosis of number 2 is most likely, or perhpas a blown capacity on the logic board. Any clicks or noise when trying to power up? Had the drive died you should at least get something, even the folder and question mark. Would be best, Clark, if we can actually find what model this is. Look on the rear for model/serial numbers.

harryb2448 said:

Well if it is a G5 it can't run Snow Leopard as that is Intel only.

I would think your diagnosis of number 2 is most likely, or perhpas a blown capacity on the logic board. Any clicks or noise when trying to power up? Had the drive died you should at least get something, even the folder and question mark. Would be best, Clark, if we can actually find what model this is. Look on the rear for model/serial numbers.

Click to expand...

Hi Harry, thanks for the quick response.

It's a 1.8 GHz machine with a serial XB413045QEU

In reply to your questions...

1. The software is one of the Leopards that is all I can say for sure.

2. It's not an Intel machine.

3. No sound or anything that I can hear (not good hearing though anymore). The actual on off switch just does nothing when pushed in or held in. It's lit as soon as the power cord is plugged in but does not seem to do anything.

Is there a fuse on the power supply to check? I can't see one so I assume I would have to pull it if there is.

What section would a bad cap be in on the motherboard? Would I have to pull the board to examine it for the normal visuals on a bad one?

Thanks,

Clark

Sounds like the power supply. Have a look at this guy's page on G5s and he may be able to help with a used power supply. Remember 1.8GHz is the original model so not worth more than say $100.00, if that.

A faster Dual Core can be had cheaply.


Bob's Power Mac G5 User Tips - Technical tips to keep your G5 working

harryb2448 said:

Sounds like the power supply. Have a look at this guy's page on G5s and he may be able to help with a used power supply. Remember 1.8GHz is the original model so not worth more than say $100.00, if that.

A faster Dual Core can be had cheaply.


Bob's Power Mac G5 User Tips - Technical tips to keep your G5 working

Click to expand...

Thanks Harry. I will pull it apart and have a look. This is a dead end machine at this time with the non software upgrades so if it looks more expensive than it's worth now or near future it may be time to scrap it and buy a newer machine.

Was hoping for a fuse or quick fix problem or even maybe a cap I could replace. So it goes.

Again thanks,

Clark

Well Clark you know the old rule with computers....there is never any 'quick fix', nor cheap either!

harryb2448 said:

Well Clark you know the old rule with computers....there is never any 'quick fix', nor cheap either!

Click to expand...

Hi Harry/All

I have run some tests on the G5. Here is what I did...

1. Tested the power supply and am getting the correct 5V at pin one on the plug. So it appears the power supply is ok unless there are other tests not listed in the Repair Manual I downloaded.

2. Tested the batter voltage. It comes out to 3.53V so that should be OK.

3. Reset the PMU button and it still won't do anything different.

4. Removed the battery and pushed the on off button. Waited 1 minute and plugged in the power cord. Same thing.

5. Removed the processor heat sinks and reset them in their slots. No change. Did not see anything that looked like it was leaking on the motherboard.

Here is what is happening now:

When I plug in the power cord I hear a click then nothing. Same when I unplug it I hear the click.

The power light on the front panel immediately lights up and will not vary from steady as soon as I plug in the power cord. No fading or blinking. Nothing happens when I push in the power button or hold it in.

No fan activity.

No chimes.

Any other suggestions?

Note: I do not have the keyboard, mouse or monitor plugged in doing these tests. Is that any kind of a problem?

This is a G5 1.8 PowerMac model 7,2 produced in April 2004 with dual processor (PCI-X). Family name A1047 model M9393

Think it is a doorstop mate!

See the G5 towers and the G5 iMac where known for these issues:

G5 Mac pro towers:

1. processor failure

2. capacitor fails

3. voltage regulator has blown

Even though the machine seems like its getting power of which it is is doesn't mean its getting enough power.

G5 Imacs: (RUN DONT BUY RUN)

1.power supply arcs off metal case burning a hole though the case causing a electrical fire (imagine this while you sleep)

2. capacitors explode (no i didn't misspell they do explode)

so you pretty much get the same results.

Honestly the only good G5 that on occasion loses a processor and has no power supply issues is the single processor G5 mac pro they rarely failed and apple just kept trying to get more speed and it blew up in there faces