G4 will not boot up about 1 in 10

[funkster]

Hi,
I have a strange intermitent problem with a G4 AGP 450 machine. About one in every 10 in just refuses to boot up. You hit the power button, the fan starts, you hear the hard drive, but there is no chime and no video at all.

One other thing that happens, when it does boot up it always spits out the CD tray (whether there is a disc in or not). Not sure if its related but thought I should mention it. Apart from this the machine works fine.

I've tried replacing the RAM and discontected all periphials.

Do you think its a dodgy power supply ?
thanks

[funkster]

oops sorry, I realise I should have posted this in the hardware section

[Rokcet Scientist]

If you can hear the fan starting and the hard drive spinning a 'dodgy power supply' is not the first thing that comes to mind, now is it...? I agree that it looks like it's probably hardware related, but it sounds more like a dodgy connection on the motherboard to me: a loose contact.
If you really need to know, I think the simplest and fastest way is to test another motherboard: shove it in and restart 20 times. If your prob doesn't reappear, it was indeed the motherboard...