Author Topic: iMac G3 500MHz (Summer 2000) CRT issue  (Read 792 times)

Offline Capt. 2110

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iMac G3 500MHz (Summer 2000) CRT issue
« on: September 12, 2018, 07:48:38 PM »
I'm not sure if this is the right place for this, so if there's somewhere better I'd be happy to put it there instead. I asked about this on the Vintage Computer Forums, but that's not really the right place for it as it's not really vintage.

I have a Summer 2000 iMac that I've owned for the majority of its life. Recently its been having some issues, mostly age related like the speakers rotting and the inner bezel cracking. But as of a few weeks ago the CRT has been acting up. The best way I can describe it is its like the red gun in the display is failing. It's bright and mostly fine for the first inch or two of the screen on the left, but after that it gradually darkens. By the right edge of the screen a bright red is at best maroon. I'd normally just say its a degaussing issue or something, but if something bright is on screen, the red will appear the right color from the border of it to the edge of the screen. I'm thinking analog board issues, but I truely don't know. Can anybody help? Thanks!

Tldr: monitor has issue with red gradually fading across screen, need to know what to fix.

Offline Astroman

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Re: iMac G3 500MHz (Summer 2000) CRT issue
« Reply #1 on: September 13, 2018, 03:17:34 AM »
Iirc these tubes are a hell to service/adjust - you need proper gear and knowledge.
(and it's dangerous for mechanical and electrical reasons, as you probably know)
At least I can assure you that back in the days we exchanged all such tubes with replacement parts.
Not even the guy with full TV service education would touch them.

If you used your iMac on a regular base it may well be just the natural wear out.
Best approach would be to pick one from trash/private sale that spent most of it's time on attic and exchange the tube (if you cant't part for emotional reasons)
Assembly isn't too complicated, but if you remove the high voltage cable from the tube be extremely careful: the inside of the tube keeps a 20kV load for a very long time.

You may also consider that burning tube circuitry may permanently pollute your home with dioxin, when the thing may blow up due to age.
I'd rather switch to a G3 B/W, which is very affordable and at least kind of similiar in style.
Turn the oldie into an aquarium or something similiar ;)