My iMac G5 w/isight display stays black on start up

Question

This all started yesterday when I put my computer to sleep and came back to wake it up. While away my computer actually turned off and when I hit space to wake it it rebooted with no display. When I try to start it up it makes the start up noise, fans run, makes normal computer noises. The mouse also lights up and the Caps Lock button on my keyboard flashes as it normally does on start up. But no picture on my display. I've tried resetting my PRAM by holding command, option, p, and r, on start up and it did make my display work one time. But I put it to sleep again after using it and when I came back it did the same thing, displays nothing. I've also tried holding in the power button until it makes that Atari noise and all that does is makes my fans run overly hard and the only way to stop that is to unplug it otherwise every time I try to start up the fans run overly hard. If I unplug it then it goes back to sounding like its working right but displaying nothing. I'm wondering if there is anything I can do to fix this? Does it sound like my display screen is dead, something wrong on the logic board maybe? I really have no idea. My operating system specs may be a little off, I don't quite remember what it's updated too, and I cant check, but know I am running Leopard.

Answer 1

If it would be a problem only with the display, it should still boot from disc or hard disk, but since it does not appear to be reading the disc (other than identifying it) I'd say it is a logic board problem.
There is three different kind of iMac G5's, the vanilla version, ALS and iSight. Vanilla has Nvidia graphics card, ALS has Radeon 9600 series card and iSight has X600 and is easily identified because of the iSight webcam. With vanilla iMac G5, the capacitors are very common issue, faulty capacitor is usually easy to identify by just opening the case and looking if thosa can-like things look bulged or otherwise damaged, their top should be perfectly flat. With ALS and iSigh -models it is very often an issue with the graphics card when solder under the chip cracks and the chip is not properly connected to motherboard. This cannot be identified by just looking which makes it difficult. Some iMac G5's also had bad power supplies in them which caused Apple to initiate recall but I don't remember which models were likely to fail.
In case of capacitor issue, they can be changed relatively easily. With that soldering problem, it is more difficult without the right tools, iSight also has different and more difficult case design in terms of taking the machine apart. Blowing some hot air (which reflows the solder and forms connection again) with heat gun may be provide short term fix or of course if you have luck, it will last until something else breaks.
Of course testing with know working RAM is the first you should do.