Welcome to the MacNN Forums.

Microfracture · Sep 7, 2007, 08:21 PM

Hello.

I have a 600Mhz G3 iMac and I have run into a bit of a problem with it.

A gradient has recently appeared on the screen resulting in the left side of the screen being completely normal while the right is greenish in color.

I really do not want even think of getting rid of the computer at all as it works perfectly aside from this issue.

Does anyone know what is causing this or how I could go about repairing it?
Any help would be greatly appreciated!

lpkmckenna · Sep 7, 2007, 08:25 PM

I had this problem, way back in 2000. Had to get it repaired, but it didn't require replacement parts.

seanc · Sep 8, 2007, 07:14 AM

Move any speakers or magnetic devices away from the computer and see if it goes away.

Koralatov · Sep 8, 2007, 04:01 PM

It's one of two possibilities. Either the colour-mask has shifted, which is unrepairable short of replacing the CRT and would cause the green, or there's magnetic interference (possibly from a speaker) nearby.

The good news is that if it's magnetic interference, and it's not been going on too long, all you need to do to get rid of it is move the speaker. Unfortunately, if it's been happening for a while, it might be permanent. That happened to a friend of mine's TV: his flatmate's speaker was directly behind the TV on the other side of (an admittedly paper-thin) wall, and it caused a greenish-blue tint to appear on one side of the screen. Unfortunately for him, he left it for a while, and it became permanent.

If it does turn out to be permanent, your only real option would be to pay an extortionate amount to an Apple Service Centre or buy another iMac and transplant the screen, which is slightly complicated. If it does turn out to be permanent, and you decide to replace the CRT, I can give you a copy of the appropriate Service Manual, if you want it.

rubaiyat · Sep 8, 2007, 04:49 PM

I am not sure how this is done on an iMac but you need to degauss it which is essentially give it a magnetic wipe by a quick electric surge.

DO NOT try to wipe it using an external magnet this is what causes the problem. You have magnetised a part of the monitor which is deflecting the electrons and causing your color cast.

To find out how to properly degauss it, look to your manual or go onto Apple's support forums and look up your model for user recommendations or for a downloadable manual or tech sheet on the subject.

Microfracture · Sep 9, 2007, 01:15 PM

Thank you for all the replies.
It look like the tinting may be permanent as it has not faded at all.

Koralatov: a service manual will be greatly appreciated. Thank you.
My iMac is a slot loading M5521 if that helps any.

I think I am going to see if I can find a parts machine on eBay and swap the CRT out.

rubaiyat: Thanks for the reply. The iMac is supposed to auto-degauss itself from what I understand. Unfortunately, it does not look like there is anyway to 'force' the system into doing it.

Once again, thank you all for your assistance.

Railroader · Sep 9, 2007, 01:46 PM

I wouldn't mess with it. You can find one another one for around US$75.

rubaiyat · Sep 10, 2007, 11:07 PM

I agree with Railroader, where I am they are even cheaper, in fact almost giving them away.

Have you tried accessing the insides of an iMac even to install a new battery?

It is an exercise in frustration and an enormous time waster even if you know what you are doing.

If you do go ahead (I strongly suggest don't) be extremely careful and discharge any residual electricity in the monitor to a grounded object such as plumbing. Work in the kitchen and ground yourself and the computer to the sink tap, it is connected by copper piping to the ground outside and will get rid of any charge.

Koralatov · Sep 12, 2007, 06:34 PM

Originally Posted by rubaiyat

Have you tried accessing the insides of an iMac even to install a new battery?

It is an exercise in frustration and an enormous time waster even if you know what you are doing.

Thinking about it more, rubaiyat and Railroader may be right—replacing the CRT might be a really work-intensive, and potentially dangerous, task. You'd probably save yourself a lot of frustration getting a new one and then just transplanting the hard-disk, Airport card and any RAM upgrades you may have in there. That way, you get a new computer, with everything as you left it on the old one, because of the hard-disk transplant. Changing the hard-disk isn't actually that hard—you can do it in about fifteen minutes if you know what you're doing. I've done opened and closed my iMac G3 about six or seven times in the last two weeks, and it's not really that big a deal.

Another bonus is that you could get a different colour of iMac too, for a bit of a change. The 600MHz came in Blue Dalmatian, Flower Power, Snow and Graphite, so you have three colours to choose from that are different from your current one. I'll likely be looked on as mad for saying it, but the Blue Dalmatian is actually quite funky, and I rather like it. I really need to give it to my friend soon or I fear I may end up keeping it...

Microfracture · Sep 12, 2007, 10:34 PM

The VGA port in the back of the iMac has been a blessing.

I decided against the CRT swap and I am pondering setting the iMac in a corner and just using it as a file server for now. I will probably buy another iMac and swap out the relevant hardware later this year.

I took the opportunity to replace the iMac with something I have always wanted.. a Power Mac G4 QuickSilver.

Koralatov · Sep 13, 2007, 06:54 AM

Originally Posted by Microfracture

The VGA port in the back of the iMac has been a blessing.

I decided against the CRT swap and I am pondering setting the iMac in a corner and just using it as a file server for now. I will probably buy another iMac and swap out the relevant hardware later this year.

I took the opportunity to replace the iMac with something I have always wanted.. a Power Mac G4 QuickSilver.

I think, on balance, you probably made the right choice. Making it into a headless server would be quite cool, though.

Good choice of machine there, by the way. I've always fancied getting my grubby paws on a a Quick Silver. Which speed did you get?

Microfracture · Sep 13, 2007, 07:47 PM

Originally Posted by Koralatov

Which speed did you get?

It is a 733. I will probably upgrade the processor with an 1.2GHz OWC Mercury Extreme at some point in the future.

Luckily, that will be the only upgrade I will need to actually pay for. I had some spare parts laying around which enabled me to max out the memory & add a 120GB drive.

rubaiyat · Sep 13, 2007, 08:35 PM

Be extremely cautious about upgrading CPUs, especially from OWC.

The older case and fans tend not to be built for the greater heat of the faster chips.

Mine overheats regularly and OWC went from extremely reluctantly returning my emails to positively unfriendly in the end. I'm stuck with it.

An expensive lesson which I shall never repeat.

There is really no good argument for upgrading, especially older machines as all the componentry is so dated that upgrading anything except drives and memory is just false economy.

If you must, buy a good quality 2nd hand machine or recent model when Apple marks down the price.

Microfracture · Sep 13, 2007, 11:13 PM

Hmm.. You definitely have an excellent point. Thanks for the heads up regarding your problems.

I was looking at it more as a relatively cheap way to boost performance and bump the processor specs up enough to meet (or rather exceed) the minimum requirement for Leopard.

The upgrade definitely isn't something that I absolutely *had* to change within the system. To be honest the 733 is just fine for what I do (e.g., web browsing, IRC, etc).