Imac G3 CRT screen problem (Not Firmware related)

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dogtanian's picture
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Imac G3 CRT screen problem (Not Firmware related)

Hi folks,

I have a slot loading indigo Imac G3 500Mhz running 10.3.9, 500Mb ram, 80Gb HD, Firmware 4.1.9 which i recently bought from a friend of a friend.

My problem is the screen almost always looks like the red is missing (very pale green in colour), at startup the screen will go either red or really dark then turn a pale blue. Sometimes if I leave the imac running for a few hours the screen seems to sort itself out with the occassional random flicker of colour.

I have plugged in an external monitor to the vga port and it works perfectly but i dont want my mac to act purely as a hard drive.

I have downloaded service manuals and was all for dismantling the bloody thing but I am massively concerned with going near the CRT for fear of death.

I really need to fix this as it makes using my mac extremely annoying.

I am at a total loss with this and any help would be much appreciated.

madmax_2069's picture
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ok go here http://home.earthl

ok go here http://home.earthlink.net/~strahm_s/manuals.html and scroll down to where it says Utilities and click on the the 265k next to Display Service Utility 4.2.1 you then can adjust every color, tint,hue, and brightness to the monitor this should fix it you have to set it all your self tho. you might find some settings to go from on the net you can adjust every thing that has to do with the monitor. and go here and read up on this problem http://faq.arstechnica.com/link.php?i=1826. i see your running os x is there any way you can boot into os 9-9.2 cause you might need to to use this utility. also go here and read all 3 pages on this site to adjust the screen in os x http://www.computer-darkroom.com/colorsync-display/colorsync_1.htm
i also have another d.a.u. i cant remember where i got it from its called display adjustment utility 4.2 its for os 9-9.2 have fun i know i did adjusting every thing on this beige G3 aio

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I'm not sure how much help ad

I'm not sure how much help adjusting the colour through software will be if the red gun isn't firing.

The iMacs have notoriously bad CRTs, judging by the number of threads we see here, though it's usually the flyback that goes.
Monitors in general are poorly assembled, and all it takes is one cold solder to create the problem you're describing. Now it may be something more complicated, but you'll never know unless you get in there and have a poke around.
The chances of zapping yourself are exaggerated as long as you're careful and don't go poking the flyback with a screwdriver or lick the anode.
You might want to read [http://www.repairfaq.org/REPAIR/F_monfaq.html]Here[/url] for some monitor background, which has info on discharging the CRT (note that most modern CRTs will auto-discharge, so doing your own discharge isn't a dramatic event).

Just a thought off the top of my head for everyone...were the iMac CRTs were so flaky compared to other CRTs, or is it that the AIO form factor has made replacement a more costly issue that we hear about it more often (ie- no one's going to bother posting here 'Help! my 15" Samsung won't turn on! I've got all my, er...pixels stored in it!')

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yea first id just try the sof

yea first id just try the software route i put a link in there that say's how to adjust the screws on the the monitor it tels you what to turn and what you need to adjust it. it is the second link in my post

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I will try the software option

Thanks for the advice. I will try the software option first, although I am not convinced that it will work. I will keep you posted.

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He he I could picture some po

He he I could picture some poor fella licking the anode of a CRT

LOL

*Lick* ZAAAP!! Thump.. "Mumbling"

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thats not right that is wrong

thats not right that is wrong on so many level's lol but it would be fun to see. i hope it can be a easy fix hope its not a cold saulder

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I tried the software option w

I tried the software option with no success, so i stripped it down and found that the rgb cable connection at the motherboard was the problem. When i wiggled the cable the colour flickered from good to bad. I disconnected it to check the pins and they were all good order, so I plugged it back in and the colour is perfect now and I also managed to not kill myself.

I just hope it lasts!!

Thanks for all the help. I am a very happy man now!

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Congratulations, glad it work

Congratulations, glad it worked out.

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sweet im glad it wasnt somthi

sweet im glad it wasnt somthing worse like a cold saulder. i am real glad to hear you getting it to work

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The screen has started to fli

The screen has started to flicker again!

I could always get a wooden kebab skewer and prod the cable through the vents in the casing when the screen starts to flicker. Not the safest option though!

Does anyone think it would be worth replacing the cable or do you think it could be the connection on the motherboard?

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replace that darrrn cable...

arrrr... back to the pirate language session, matey! ... i should smoke less, then my head would probably get enough oxygen... *narf*

anyway, back to topic: i would replace that cable. i had at least 2 (maximum 3) of those imac's here in repair, all of them with the same problem that the screen was tinted and sometimes didn't work at all. after replacing that rgb cable everything was fine.

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It could be either, but you s

It could be either, but you seem to have effectively narrowed it down to the two.
If you've got a soldering iron, you could try melting the connection to the motherboard.
Or you could try - if it's possible in that small area - wiggling just the cable around, and keeping the connector as still as humanly possible. If you get more colour jumps with the cable, then I'd say that's your problem spot.

A more 'ghetto' solution might be to find a position of pressure on the cable where there's no colour jump, and use a shim, cable tie, etc. to pull and hold the cable in that position. I bought an IBM 17" monitor that came with a C-clamp attached to the back of the case, pulling the cable in one direction. As long as that clamp was there, the colour was perfect (it turned out to be a solder joint on the connector, which I fixed. Six years later, my Dad's still using the monitor, and I got a free C-clamp)

(edit) Chris501, what's at the other end of that cable? I never traced it back when I had an iMac.

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lol i guess i spoke to soon

lol i guess i spoke to soon

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My iMac g3 400 slot screen probs

I got this tangerine one and it hd a pink hue that was nasty. I used an external monitor and then I tried to fix the iMac. I took apart the tray from the monitor, cleaned it all up and then went through the parts and checking every connection around. I reassebled it and added more ram.

Then I installed a 10.3 and followed its instructions. When I restarted it I had a numer of updates to install. When I finished with that process, It was back to normal. The colors are correct but the brightness is still just a little bit off. It did not cost me any money since I had the parts on hand from other iMacs.

Good luck. I believe my solution was a software problem. Funny huh?

Peter

Jon
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Did your need a firmware upda

Did your need a firmware update to do the 10.3 install? That can cause all sorts of troubleif it isn't done, and that's why the OP had made a point of it in his title. I'm glad he did, 'cause that saved us a lot of "Try the FW update!" posts. Smile

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Thanks for the advice. I wil

Thanks for the advice. I will try replacing the rgb cable as I am not a soldering guru.

Does anybody know where I could source an RGB cable from bearing in mind that I am in Scotland?

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imac G3 monitor problem - dark...too dark

Hi ya'll

So I have had a G3 dv se imac (550 mhg, 30gb hd, 250mb RAM) for about 5yrs and within the last month/month and a half the monitor has gradually dimmed itself to the point of, where now I can only see things with as much contrast as black on white word processing. This is a great computer...if nothing else it will suffice for homework and web research but I really need to figure out how to fix this.

Then like a total idiot...I've been looking for several weeks on Craigs list for a similar unit to replace mine in case its to far gone. So anyway, I finally find one for $100, comes with 2 printers, two routers, and a CD burner. It only has a 10gb hd, so I get on and order a great 100gb internal hd for $50...thinking even that is a great deal. I get the computer home, my brother installs the hd, office, adobe CS2...I get on it finally for the first time and, omg, the monitor appears to be at the same place that my totally dark other computer was about a month ago. I didn't realize it, or I guess didn't even expect to realize it, so I didn't look for it very carefully before now but crap dude! And I suppose to someone that doesn't know about it, it would go completely unnoticed for quite a while, especially with nothing to compare it too...but I know, in a matter of no time at all, it will be to dark to even use.

Does anybody have any ideas?...for both of them? I know I can get an external monitor and just use these as hd's but I don't want to do that, that's a waste and will cost more money. How much do you think it would cost to take them in and have them fixed at a repair shop? Please help...I need something that works...I'm about a week and a half from the end of the quarter and I need something to use to finish my graphic design final. I'm in a wheel chair...otherwise, I'd just go to the lab at the college.

Thanks, Kelly

Jon
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This really should be it's ow

This really should be it's own topic, but anyway... Wink

Has yours had the firmware update? Some iMacs can run without it, but they will have overstressed video circuits that will fail over time. If that isn't the case, then you can probably adjust the flyback voltage or some of the other tunings as described in the Service Source manual. Don't try if it's too unknown for you, as the flyback can pack a mean (and possibly fatal) punch if you go at it without a certain amount of knowledge and respect.

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