Apple G4 Power Supply Woes?

Predius asks: "I, like many others based on forum hopping, have an Apple G4 desktop that has decided it no longer wishes to power up. I've replaced PRAM batteries, verified power supply voltages, pressed the CUDA switch, and done combinations of the above. Trying to start it just results in a blip of the powersupply fan and the power led on the motherboard flashes once. Every now and then it will actually boot, and when it does it's 100% rock solid, will reboot fine, etc. If I power it off, I get to play games again trying to power it up. Does anyone know how to manually start an Apple Gigabyte or later rev power supply? Standard ATX power supplies can be fired up by shorting the green PWR ON lead to ground, but Apple decided to be different. I await the collective's wisdom."

Comments

Obvious?

[YouHaveSnail]

I hate to ask the obvious, but since your machine is clearly working improperly in a manner that cannot be due to software, OS installation, disk formatting, etc....

Have you considered taking it in for service?

The friendly folks at the nearest Apple Store will be happy to take a look at it. If it's still under warrantee, or if you've invested in AppleCare, it won't even cost you anything.

Re:corrupt PMU?

[bluethundr]

Pop that sucker open (unplug first!) and there should be a little black button on the lower front of the logic board. "Reset pmu" will be printed on the board somewhere near the button. Push it for one second and only press it once. Let the box sit for roughly 5 minutes unplugged and then turn it on.

That sounds like the procedure we used to do on the old pre-blue-n-white PPC macs. Is this 'PMU' button another name for the CUDA button? I haven't seen a mac motherboard in a while. Even the most knowledgable mac guy I've ever known couldn't tell me what CUDA stood for, however. Generally I've known that this is a good idea to do after installing new ram and whatnot, but I am a little unclear about the function of the CUDA button. Except that I've heard it described as a "deep pram zap".

Re:Aggravating problem

[Graff]

I pulled those fans out and they looked like they could be replaced by standard, quieter fans. I took one from the last PC I'd built...

I noticed the apple supplied heatsink was BURNING hot...

I ditched that heatsink...and replaced it with a Zalman flower...The heatsink for the G4 attached differently, but it was easy enough to adapt the zalman with insulated wire tied underneath the CPU board...

the powermac booted, and stayed working far longer. For about three days, and from then on it wouldn't boot...

It turns out because I had MODIFIED the computer that my warranty was void. wtf? I added a superior cooling system to the machine, quietened it, IMPROVED it in every way, and they deny my claim?

OK, let me get this straight. You took a perfectly functioning computer for which the only problem was that it was loud. You replaced the fans on that computer without making sure that the replacements had the same airflow. The computer overheated so you got a completely different type of heatsink than the one that came with the computer. The heatsink didn't fit but you retrofitted it onto the processor. Then computer went completely belly-up. Face it, you didn't improve the computer in any sort of way, you made it worse and it malfunctioned.

Now none of these parts were approved by the manufacturer and I'm pretty sure that you are not a certified Apple technician, yet you still expect the store you bought it from to fix what you messed up. There is pretty much no company out there that would take back any product treated in this manner. If you retrofit stuff be prepared to pay for any mistakes you make, that's standard in any industry.

I'm sorry you had to learn this lesson the hard way but that's the way the world works. Don't blame Apple for your foolishness.