iMac G3 video card repair? please help

Upgrade your video card? Not in an iMac my friend, unless you can get your hands on a used logic board.

Could be problems with the CRT electronics, there's some areas with hints on repairs and common part numbers.

Don't know where I last saw it.

If it has a VGA out port, you can usually eliminate the video chip as a problem really quick.

Because if it is the video chip, the computer logic board is dead.

Good chance that you'd plug in a new logic board and still have the same problem.

You can do a search of CRT iMac Repair and come up with a bunch of sites that talk about the CRT electronics going bad.

Sites like http://www.macopz.com/columns/imacrepair/index.html

There should be some troubleshooting resources, or ways to check the logic board (since some people remove the board from the machine when the CRT dies).

But if you want to replace the logic board, before searching more on the iMac common problems.

I won't stop you.

Could be as simple as interference from other things around it. Make sure it isn't near other equipment like speakers, radios, phones, fluorescent lighting, magnets, or other electronic equipment. There was also an issue with the RGB cable that Apple's official position called for an authorized repair person.

As far as the VGA out, look under the access panel towards the rear of the machine (not the one where the RAM is located). I think most slot-loading iMacs came with a VGA port there.

Originally posted by K12MacTech
As far as the VGA out, look under the access panel towards the rear of the machine (not the one where the RAM is located). I think most slot-loading iMacs came with a VGA port there.

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Underneath a door/panel by the power cord.

Originally posted by slipper
so what could the problems be?

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According to the troubleshooting charts...

No Video or Unstable Raster

Corrupted PRAM.
Corrupted system software.
The PMU chip or logic board needs to be reset.
Bad video cable connection.
Bent CRT neck pins.
Bad power/analog/video board
Bad logic board
Bad internal RGB video cable.
Bad power/analog/video
Bad CRT.

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If you want to read the trouble shooting charts, use the darn link in the PM.

You can also look at this apple article:

http://docs.info.apple.com/article.html?artnum=31262

Not much info for the average user - if you are a service provider it would show more detail, but it does show there was a known issue with those iMacs, and the resolution if you take it to your "Authorized Service Provider" was to replace the screws on the RGB cable.

In one instance the suggestion to move the iMac actually helped me. The system with the problem was located right next to a microwave oven which caused the interference. I always like to try the simple solutions first.

You may also find some comments/resolutions if you search the Apple Discussion boards searching with keywords like wavy or flickering display. There was quite a uproar there before Apple admitted there was a problem.

i had an old imac that did this. apple took it in for testing and told me it was the logic board. yuuuck. i'd get all your important info off the hard drive and save the money from the fix and buy something new.

Originally posted by slipper
and what would i be doing with this VGA output? connect it to a different monitor? sorry i and completely unknowledgable with comps.

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You want to replace the logic board without doing a simple test, connecting a computer monitor to the iMac's VGA out port, because a PC owner said your video card is bad.

All I'm saying is iMacs tend to have problems other than a logic board causing wavy video. (ie, that link I left above). Though it was "supposed" to be reengineered on the slot loading machines.

Use Google to search for sites that tell you how to troubleshoot to a specific board on your iMac. (logic board, down converter board, the power/analog/video board, CRT neck board. or the RGB cable)

Download the manual from the link I PMd you. That will step you through the troubleshooting chart.

Though there are people who didn't want to do any of the above, and simply put their iMac logic board in a PC case and used a external monitor. And there are sites for that also.

But it can be something as simple as choosing the wrong frequency when you changed your screen size to moving something next to your machine (or on the same breaker) causing CRT to go crazy.

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It may be the logic board, it may not.

Battery?

This is a shot in the dark, but I have an imac Dv+ (g3 450) which has been humming with inreasing frequeny lately. the last time I had this problem, my 6100'd moniter needed the battery replaced. Your screen going blaNK makes me think your moniter battery is dead, I have no idea how hard it is to replace on an imac CRT, but a new battery won't be expensive if that is indeed your problem. I really don't know why it needs a battery, or if they even still use batteries but I do know that I USED to have to replace it every three or four years or so. hopefully someone who really knows about moniter batteries ould lear this up.