Hey guys,

I have a Power Mac G4 (Digital Audio) that refuses to start up.

Power button does literally nothing.

No light, no sound, no fan, no nothing.

Checked PSU and it is delivering 0 volts.

I will try to modify an old ATX power supply to work with it....

But is there anything else it could be?

PRAM battery seems OK (3.6V out of the holder, 3V in the holder)

Did you try resetting the hardware PMU by pressing the small button near the PRAM battery ONCE briefly. If you're not sure that you pressed it, don't press it again until ~15 seconds have elapsed.

If that doesn't fix it, replace the PRAM battery if it is more than five years old.

Some people also have had problems with the little board where the power on button is.

I would check these items first before I start to think about replacing the power supply.

I did

When it didn't do anything I may have pressed it twice quickly. What happens if you press it many times?

I tried shorting out pins in the socket where the front panel connects to, no effect

Finally I measured 0V across several PSU wires. It could be the PSU but I hope it's not.

From what I have read, no personal experience, if you press the PMU button more than once in quick succession, the circuit can go into free running oscillations and will thus drain the battery very quickly - but don't quote me on that.

I had, actually still have, a G4 where I had to push the PMU reset button every time to get it to start up.
I just left it running and eventually switched to a Mac Mini. The G4, even with a faster dual CPU was just too slow for what I needed and a lot of software was no longer supported on the old machine.

I have a DA with a bad mobo,

What area are you in?

Near montreal.

Unplug your computer and take the battery out, and leave it out overnight. That should clear out everything.
Put the battery back in the next day, plug it in, and pray.
Sounds like a bad power supply though.

Here are some more tips you can try before replacing the power supply.
Power Mac G4 Power Supplies

And there is a fellow in Montreal on L-Acadie who may have a used power supply for your Mac.
He works out of his apartment - replaced the screen on a MacBook Pro for me - very reasonable and it works fine.
Replacing a power supply is a piece of cake compared to replacing a laptop screen.

Greetings y'all!

My G4 Digital Audio is also exhibiting the same symptoms- refuses to power on (I tried swapping out power cords and the PMU reset). May very well be an issue with the power supply too.

Anyone know if the fellow on L'Acadie still works on Macs / still in business? Would really hate to scrap the G4.

The guy on l'Acadie has been in business for a few years, no reason why he shouldn't be any longer since he just works out of his apartment.

I had his card but don't know where it is right now. look on Kijiji or Craig's List, that's how I think I found him.