G4 Cube shows strange behavior when powering on (and eventually fails to boot up)

[EmilioCube]

My Cube recently just didnt want to boot up.

When I touch the power button, its light goes on, the red one on the motherboard as well, the HDD starts spinning, but I dont get a chime and the power buttons light stays at the brightest level (normally it goes only so bright when you touch it and dimms after touching it). 5-10 seconds after powering it on, the power light blinks 5 times in rapid succession and another 10 seconds after that the Cube shuts itself down.

I disassembled the motherboard, graphics gard, RAM, VRM, CPU and IDE cable from each other and cleaned the connectors, but that did not work. Since the last time I booted the Cube up successfully (one day ago) I havent changed a component in it. At least nothing exploded or smells bad like what happend with my VRM.

Does somebody know this phenomenon and knows what I can do next?

 

[Bigwaff]

Power Mac G4 Cube Troubleshooting

The PowerMac G4 Cube is a compact personal computer from Apple Inc. It runs on either a 450 or 500 MHz processor with a selection of graphics cards like ATI...

www.ifixit.com

 

[ervus]

... the power buttons light stays at the brightest level...

Those capacitive touch buttons can be a bit, touchy. It could be that it thinks you're holding the button down. You could disconnect it and power the Cube on a different way and see what that does.

 

[EmilioCube]

Those capacitive touch buttons can be a bit, touchy. It could be that it thinks you're holding the button down. You could disconnect it and power the Cube on a different way and see what that does.

Mhh, I tried it with my second power button as well and it shows the same behaviour…
Guess I’ll try connecting it for powering on and then disconnecting it.

Power Mac G4 Cube Troubleshooting

The PowerMac G4 Cube is a compact personal computer from Apple Inc. It runs on either a 450 or 500 MHz processor with a selection of graphics cards like ATI...

www.ifixit.com

First I was like „How could I be so dumb forgetting about the RAM“ but I’ve swapped my RAM and that still doesn’t work. But thanks for the link, haven’t known that iFixit also has some Cube related articles.

 

[EmilioCube]

Leaving the power button disconnected and plugging the Cube in let’s it behave as before: HDD spins for 20 seconds, then stops and accelerates agai, repeating that over and over.
But I found out that only if the original 20GB HDD is plugged in, this behavior shows up. Unplugging it and booting from the Tiger Installation CD works fine. I also tried installing it on a new SSD but it also does not get recognized. That makes me think something with the ATA cable is wrong. Other ideas?