Mac G4 power supply failure/solutions?

[Baxter Bradford]

Suddenly tripped out whilst working, all the lights went out, no crash sign etc and a reboot started it working again. Prior to this it had been a bit unstable today with 3 or 4 crashes needing a restart.

All fine after the power tripping out initially for another couple of hours, then tripped out again. Cannot get it to reboot, no power light on button etc. Have checked connections, changed power lead, socket etc all to no avail.

Am I looking at a new power supply unit, is there somewhere in the unit that there is a fuse which commonly goes etc or somewhere that gives diagrams/advice on the net please?

Am about to have exhibition and need to print out a couple more images, from the HDs in the G4; this situation isn't ideal!!!

If push comes to shove, could retrieve HD and put into one of those external cases to get image files and drive from this Macbook Pro.

Many thanks

[bsimison]

Which G4 model is this? Some were better than others, and a few had chronic power supply problems.

First thing I'd check is the motherboard battery. Check the battery output with a voltmeter. If it's substantially less than 3.6V, get new one.

If it's not the battery, you may need to source a new power supply. Either way, I'd get an external drive enclosure and transplant the HD to meet your deadlines.

[Baxter Bradford]

Thanks Brett

It is a 1.25GHz Dual Mirror doors (not FW800). Coincidentally I have just changed the PRAM battery a couple of weeks ago, a half AA sized one. Is this the one you mean? The reason I changed was that the machine seemed to be losing settings.

[bsimison]

Yeah, that's the battery I was talking about. If you've just changed it, something else must be wrong. It's a safe bet that the power supply has gone bad.

A few things to try:

Disconnect *all* peripherals (except keyboard, mouse, monitor) and try to boot.

Open the access door and find the PMU (or "CUDA") reset button. It's a tiny, 3mm-diameter black button, usually next to the power supply. Press and hold for a couple of seconds then try to boot.

Open the access door, leave it open, and try to boot.

Check your RAM and make sure it's all firmly seated correctly.

Remove your RAM and install one chip at a time. Try to boot with each chip.

I've got the repair manual for that model on a disc somewhere. I'll see if I can dig it up.

-Brett