G4 Quicksilver won't power up

've got a friend with a G4 733Mhz Quicksilver Power Mac.

She had a stick of 128Mb and 256Mb RAM in it and fitted another stick of 512Mb RAM.

When she powered up, OS X couldn't recognise the new 512Mb.

She turned it off, took out the new stick and turned it on again.

It now only whirrs for about 5 seconds before it powers down.

So far she's tried:

• pressing the PMU button
• taking out the battery, leaving it, putting it back and pressing the PMU button

Every time it just lasts 5 seconds before turning off.

I'm going to try and fix it in a few hours, but does anyone have any suggestions?

may wanna try booting up in safe mode (hold down SHIFT while booting up). then, if you have the original disks, do a hardware test. that will see if the RAM is the problem or if its something else. good luck.

p.s. also could be a power source issue. but maybe try the above first.

I've got the machine and taken it home. It only stays on for about 2 seconds before powering down, so no time for booting into safe mode. I've tried disconnecting and connecting the power cords - the lead to the logic board works (if you disconnect it, it won't power on at all).

The only other thing I can think of is the battery. The behaviour is the same, with or without the battery in, so it could have run flat. I've ordered a new one, so we'll see if that works.

No luck. A new battery made no difference.

Any ideas?

A new battery fixed mine with much the same problem

The only other thing I can think of is to put each ram stick in one at a time to see if any of the sticks will get you to boot up

Thanks for the reply. I've tried that but no luck. Messing about with the battery causes it to not respond at all. Then pressing the PMU button makes it power up for the two seconds before turning off again.

I think the logic board is fried. I bet my mate did something stupid like mess about with the memory with the power on. I'm really ****** off though because I sold it to her for £180 and then she goes and breaks it.

G4 power up problem

Does the red light illuminate on logic board at power up? If so do you get chime at start up? If so hold option at start up and wait screen will appear showing any functional boot drives, if it does choose which drive to boot and click the arrow, if no drive shows try a new drive and run disks if no disks message me and I can walk you through setting up for test. Also you may possibly need to reset PRAM by holding P R option and command at start up and continue to hold until 3 chimes are heard then release.