iMac G3 Blank Screen Issue

[Strimkind]

I am busy working on this iMac G3 Rev A Tray Load. It boots up fine and a picture comes up but as soon as it starts to boot into the OS, it goes black. Now this does not happen all the time, just most. I have tried it from a hard drive with 10.3.9, a CD with 8.5, 9.0.4, 10.2, and 10.3. The power button stays green when it does this and you can hear it doing something...kinda like it was switching resolutions but it was not working.

I have no idea what is causing it. I have used the Cuda switch on the logic board, checked the RAM, and reset the NVRAM.

Could this be caused by a bad analogue board or some other issue?

If this is a bad analogue board, I was thinking of gutting the PSU and the logic board and creating a headless iMac.

Anything you guys have to offer is appreciated.

 

[LCGuy]

The best way to find out would be to plug in an external display. Take the bottom off, unplug the DB-15 connector, and then connect either a multisync vintage Apple display, or a VGA adapter and VGA display. If you get an image on the external display (the internal display will remain dark and the power light amber because the display's not getting a signal) then its a display issue. If you still don't get an image on the external display I'd be looking at your RAM/VRAM, or perhaps the slight possibility of a busted GPU.