Imac G3 sometimes flickers and dies

Hi there! I recently bought an old ruby Imac G3 off ebay. The only problem thus far is that every now and then the screen will begin to flicker drastically and sometimes completely blacken out. I'll then have to unplug the computer and turn it back on. It doesn't happen very much, but every now and then it does. This issue occurred before and after I installed an internal DVD drive(so I know the fact that I opened up the comp doesn't have anything to do with it). Also, I attached an external monitor and the flickering issue doesn't occur on the external when it does occur on the internal. I'd be fine with using the external for extended periods of time-especially to watch DVD's, however, when the screen on the internal dies after the drastic flicker, it causes the hard drive to sleep kinda-so the external display will disappear as well. I've heard of no ways to disable the internal monitor while enabling the external-so that's a no go as far as I know. Is it the logic board that needs to be replaced? I'm kind of new to all this computer stuff. Any suggestions or ideas? Thanks!

Long story short is the CRT display or one of the components for the CRT display is going bad. The flickering you're experiencing will only get more & more frequent until eventually the CRT display will be unusable.

That's just they way it is with an approx. 10 year-old iMac with a built-in CRT display.

- Nick

And sadly no repairs for a CRT screen. Only suggestion is check the firmware has been updated to version 4.1.9 as an older update can cause screen problems:-

http://discussions.apple.com/thread.jspa?threadID=121823

Aww.... Yeah. CRT's going. You might be able to get more life out of it if you keep brightness to a minimum. But eventually "Probably within a few months" That little iMac is gonna see it's last day. ;(

On a slot load you can unplug the video cable on the top logic board..thats under the ruby
cover. You have to take the front bezel off then the cover to get to it. Do Not Touch the high volt lead to the picture tube. Then it will just out put to the external monitor.

Mac SK said:

On a slot load you can unplug the video cable on the top logic board..thats under the ruby
cover. You have to take the front bezel off then the cover to get to it. Do Not Touch the high volt lead to the picture tube. Then it will just out put to the external monitor.

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Any more specific directions on how to do this? For now i'd be okay with switching off the internal monitor and just using the external. I'm just afraid i'll mess something up as I'm not too sure which one is the proper video cable. Thanks!

letawookiewin said:

Any more specific directions on how to do this? For now i'd be okay with switching off the internal monitor and just using the external. I'm just afraid i'll mess something up as I'm not too sure which one is the proper video cable. Thanks!

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Instead of waiting for a reply...why not try "Googling" this:

"imac G3 disassembly"

...you'll get an answer MUCH more quickly!

- Nick

Thanks for the help! Once I get the computer connected to the internet, i'll try updating the firmware before I take the step of pulling the cable on the internal monitor. The computer was freshly installed with MAC OSX panther before the guy I bought it from shipped it to me.

letawookiewin said:

Thanks for the help! Once I get the computer connected to the internet, i'll try updating the firmware before I take the step of pulling the cable on the internal monitor. The computer was freshly installed with MAC OSX panther before the guy I bought it from shipped it to me.

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I'm not 100% sure if most iMac G3 disassembly guides will actually include the removing of the CRT video cable from the logic board (since it may not be something most people need to do)...but once you figure out how to take apart the iMac G3 to get to the video cable (via one of the iMac G3 disassembly guides)...you will probably have no problem figuring it out...it's not really that complex in there!

In case you don't do this sort of thing very often...be very very careful working around CRT display components! Even for a while after unplugging the computer...the CRT components can & will retain a very very large electrical charge (something like up to 25,000 volts)...and if you touch the wrong thing...you won't like it very much!!!

Here's an article on how to safely discharge a CRT display:

How to Discharge a CRT Monitor

Hope this helps,

- Nick

it sounds like it could be the firmware from some other information i'm reading...that is if the guy I got my G3 from didn't upgrade the firmware before he freshly installed OSX Panther then it's possible these screen problems could be the result. I'll keep everyone updated. Thanks again!

letawookiewin said:

it sounds like it could be the firmware from some other information i'm reading...that is if the guy I got my G3 from didn't upgrade the firmware before he freshly installed OSX Panther then it's possible these screen problems could be the result. I'll keep everyone updated. Thanks again!

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Well I guess it's possible...but I doubt that the firmware is causing the flickering of the iMac display. Remember your title says, "iMac sometimes flickers & dies".

A CRT display "dying" is usually not a firmware issue...10 or more years of usage wears out a CRT display & components...and that's more than likely the issue.

Sorry...just being honest.

Good luck,

- Nick

you're right. the firmware is up to date...so that's not the problem. Thanks again!

letawookiewin said:

you're right. the firmware is up to date...so that's not the problem. Thanks again!

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The CRT or CRT components are worn out. I'm not sure what you paid for this G3 iMac...but when buying an approx. 10 year-old CRT based computer...this is one of the main things to watch out for.

I'm hoping you didn't pay too much for it...in fact you may have paid more for shipping the computer than the actual e-Bay cost (since it's relatively big & heavy). So not too big of a $$ investment. And if you're ok with doing the external monitor hook-up...then everything is still good!

- Nick

Yes, the shipping price was around the same as the actual price. So it didn't cost very much at all, lol. I have changed the display geometry to make the quality on the internal as small and low as possible while it's still nice, colorful, and full sized on the flat screen external. If the internal wont begin to mess up at these very minimum settings, using the external will do.

Thanks again!

Once repairing a slot load iMac that had been nuked and the right firmware not installed, I had to unplug the video connector to get it to output to an external monitor to see how to reinstall the firmware as the CRT did not work at all. The connector is the only multi pin that plugs to the board,right next to the power supply. You do not have to touch anything on the picture tube itself. Ive seen Mods where the whole logic board is in a box.... if you can figure out the 12 volt power leads.

Are you hearing any snapping sounds? The real old iMacs did that with a flickering display just before the Flyback Transformer (Horizontal Output Transformer) was ready to short out. I have replaced 2 of them so far here on the old Tray load iMacs.

dtravis7 said:

Are you hearing any snapping sounds? The real old iMacs did that with a flickering display just before the Flyback Transformer (Horizontal Output Transformer) was ready to short out. I have replaced 2 of them so far here on the old Tray load iMacs.

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I had one that made that snapping electric sound and the picture would narrow like an old B&W tv from the 50's. I sent it back to the thrift store when I found that green slot load on the side of the road...the one that has no firewire. I just swapped the hard drive...things were easier back in the old days. Oh..dtravis7..I really like your new icon.

Yes, I did hear the electric snapping noise at times.

letawookiewin said:

Yes, I did hear the electric snapping noise at times. It appears the internal display is completely dead now so I wont be needing to open it up to disable it. The external is still working fine and the quality is great.

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I was going to mention that I decided to take one of my iMac G3's apart to see how easy/hard to was to get to the cable you needed to disconnect. I gotta tell ya...it is no simple process! There is a lot of disassembly...and this is when Apple was still putting things together with a lot of "snap together" plastic pieces. So this makes disassembly more difficult...since the plastic pieces don't want to come apart easily...and the chances of something (plastic) breaking is pretty high.

I worked on it for about an hour (being careful)...and I still have some disassembly to go.

So if you don't have to take your G3 iMac apart..don't...unless you're curious & up for a challenge!

- Nick

pigoo3 said:

I was going to mention that I decided to take one of my iMac G3's apart to see how easy/hard to was to get to the cable you needed to disconnect. I gotta tell ya...it is no simple process! There is a lot of disassembly...and this is when Apple was still putting things together with a lot of "snap together" plastic pieces. So this makes disassembly more difficult...since the plastic pieces don't want to come apart easily...and the chances of something (plastic) breaking is pretty high.

I worked on it for about an hour (being careful)...and I still have some disassembly to go.

So if you don't have to take your G3 iMac apart..don't...unless you're curious & up for a challenge!

- Nick

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WOW Nick ...if you lived next door to me we could get things fixed. That time I had to pull off the top ..I had to to get the machine going. Taking off the front bezel is the worst. Theres all these little doors over screws and you need something thin to slide around the bezel to unlock the little connectors. And you can break the bezel real easy.