[andreas_g4]

My fathers iMac (iMac G3 400) shows it's age, I guess. The monitor occasionally switches from "normal" to "bright", meaning that one can read and see what's on the screen, but the contrast is so weak and it's so bright that you can't really work.

http://www.awernicke.de/diesunddas/macnn/iMac1.jpg

http://www.awernicke.de/diesunddas/macnn/iMac2.jpg

http://www.awernicke.de/diesunddas/macnn/iMac3.jpg

Could this problem be heat releated, since the problem occured only since the weather is hot. Or is this a cabeling problem?

Unfortunately I don't have an external monitor to hook up and to test it, but I'm pretty sure it's just a dying CRT. If so, can I replace it myself?

Edit: Come on guys.. Inline image guidlines are in the announcement at the top of the thread listing. -Misc.

[Eriamjh]

The CRT itself is probably fine. It looks like a component or two in the brightness/contrast circuit is failing and going into overdrive.

Sad, but it probably isn't worth fixing unless you know a TV repairman who can easily diagnose the component and knows how to fix it.

I'd gut the machine and put the mobo into a tiny case and hook it up to an LCD or other display to continue to use it. Or buy another iMac on ebay with a non-working mobo and do a gut transfer. Sorry. I hate to see an imac die.

[andreas_g4]

@ Eriamjh: Maybe I'll do the defect mobo -> monitor exchange thing.

But, a new aspect occured: When the monitor is in it's bright-phase, putting the iMac to sleep and waking it up a short time after often helps.

Obviously, the erratic part is somehow affected by putting the monitor on/off.

[ApeInTheShell]

Mine has the same problem and i found keeping my feet off the desk helps. Also the cold from my window makes this thing an ice cube and hand warmer at the same time

So if mine has that circuit failure it ain't going down without a fight