Semi-dead imac: startup problem

[nolem]

I recently got an old 400mhz imac g3 with firewire to play around with in my computer tech class at school. It is in semi good shape except for one problem, it won't startup... I got it to startup once, but then shut it down for the weekend(mistake). Now it won't start up.
When I press the power button, (on the comp itself) it lights up normal, but there is no usual "bong" and the screen stays black. Then nothing else happens. I cannot hear the HD spinning or anything else louder inside it, yet the power light is on.
I have tried the cuda button, refit the ram, reseting the pram doesn't work because ther is no bong, and have switched the pram battery.
Also I put a blank hardrive in (20 gig) but I don't think thats the problem...

Any suggestions would be great, I've done a search in the forum but haven't found another one like this.
P.S.: I have access to several more old imacs so if I need to swap a part it will be no problem.
Thanks

[Rower_CPU]

Wow. Sounds like you've tried everything I would have. The only other thing that comes to mind is using a different power cable and outlet, just to eliminate the possibility of a power issue.

I'd also suggest checking out http://www.macfixit.com and http://www.macosxhints.com to see if there's anything there.

[Horrortaxi]

Dead power supply? If all else fails, iMacs make swell aquariums.

[Spock]

I Have a B&W Powermac G3 that has the same problem. I had it booted up once and shut it off and nothing, it really sucks.

[virividox]

it could possibly be a power issue. if thats the case ouch, its not something you can just replace tho, kinda tough luck

[nolem]

Thanks for the suggestions, I'll try switching the power supply from another imac lying around.
I'll keep the progress posted.

[nolem]

well, it turned out to be the motherboard itself, and the only other board around is non-firewire, damn, no more blazing speed for me...;)

[nolem]

so now its a 350 mhz. Is it possible to salvage the 400 mgz chip form the broken motherboard, if the chip itself is not the problem?

[Rower_CPU]

Possibly. If there was no damage passed on to the CPU from the motherboard. As long as you have the tools you need to uninstall/install and don't damage the faster proc, it should work.

[nolem]

it looks like the cpu is soldered directly onto the board, too bad. But that is the least of my worries now that the friggin' screen is crapping out on me! This mac is cursed... now I have to swap it.:confused:

[Calliander]

It probably had a bad Logic Board and Power/Analog Video Board. Definitely not worth repairing.

[nolem]

you don't think putting a different screen in it would work? there are plentifull around my classroom.

[Toeknee]

I dunno those CRTs hold a charge for a loooong time. I dont think it would be worth trying to swap it out. Why dont you just grab another iMac and work with that one if possible... at least that way you wont get electricuted. :)

[nolem]

I know how to discharge the screen, but yeah I think I"ll start over with another one.