G4 wont turn on

Did you try all the steps here? Resetting not only the PMU, but the SMC and the PRAM.

You're going to need a keyboard ...

it should work with any keyboard , only thing is on a windows keyboard the option key and and apple key are swapped ,
means the Mac option/alt key is where the window is and the command/Apple key is where your alt key sits i think thats about the things to remember

I assume it's a PowerMac?

In that case, it's the PSU. Get a cheap ATX PSU and rewire two cables.

(MDD requires a non-ATX PSU, but even those are available as cheap PC parts)

Which one?
Graphite? (PCI-Graphcis, AGP-Graphics, Gigabit Ethernet, Digital Audio)


Quicksilver?


Mirrored Drive Doors (MDD):

Souds like a PSU issue to me. Like Giuly says it depends what model you have what kind of powersupply you need.

Before going and buying parts look for a button that looks like this (caution large pic, button highlighted by red circle) inside the the G4 (should be on the main board, the pic has it by the battery your model might not have it there.)

Press that button, close everything up and press the power button to see if it works... otherwise use the link r.j.s posted and follow those steps, then consider buying a PSU if that doesn't work.

Before scrapping, you should google quick PSU fixes. You can get a PSU that will work in the $5-15 range and it's a really simple fix...

G4 wont turn on

I had the exact same problem.I had to constantly unplug from the wall then plug back in for the power button to work.So replaced the battery,disconnected the HD,video card and drives,NOTHING. I then purchased a refurbished PS with a year warranty and installed it,same thing,power button light was on when pressed then went right off again.The fan started spinning faster and LOUDER .

Then after getting ready to trash it I decided to take out the dual processor board and reseat it.Guess what.... IT'S WORKING AGAIN !!!!!

Every once in a while it will crash,guess when that happens,whenever I CLOSE THE SIDE PANEL of the case.

I think this is a design flaw.Every time we close the case back up it needs to "Click " to lock.I've found that the logic board is jarred loose enough to make the system crash.

When it crashes,I take a bamboo chop stick ( because it's softer than a screwdriver ) and press 4 times on the two exposed sides( all four corners ) of the logic board into the mother board.Once it reseats it starts right up with zero problems.If I close it hard it crashes but once logic board is reseated it starts right up again.

I hope this helps