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iMac G3 ticking and screen distortion
Posted by: victor.muc on 2026-09-17 07:26:03
Hey y’all,

I’m having a problem with both of my iMac G3s.

I got the first one, a 1999 Blueberry, in October last year. It ran perfectly fine for months until it started making ticking sounds in March, accompanied by a very brief line/distortion on the screen. I stopped using it regularly after that and only powered it on occasionally to investigate the ticking.

Every time I tried it, the ticking seemed to get worse, with multiple weeks between each power on. The last time I tested it was about a month ago. I let it run for around 20 seconds, and it was ticking every 1-2 seconds, with visible distortion on the screen each time (always appearing as a line).

The other machine is a 2001 Blue Dalmatian iMac that I got about two months ago. It worked fine for the first few days, but then it also started ticking while in use. It doesn’t happen nearly as often as on the Blueberry, but usually at least once every 5-10 minutes, sometimes more. Sometimes it can run for 30 minutes without a single tick, but eventually it starts again.

It seems especially noticeable when the iMac hasn’t been powered on for several days. In that case, I sometimes get multiple ticks shortly after turning it on.

I already blew out the internals of my Blue Dalmatian with compressed air, which seemed to make it better for a few days (although that could have just been a coincidence), but eventually the ticking came back.

My questions are: What can I do to fix this? Is this a common issue with G3 iMacs? And is it safe to continue using them and just ignore the occasional ticking, or could that cause further damage?

Thanks so much!!
Posted by: Schmoburger on 2026-09-17 10:34:26
It sounds a lot like the flyback transformer is on the way out. That ticking is a momentary HV electrical arc, which happens when the transformer's insulation breaks down over time. Sometimes if the anode cap has degraded and isnt sealing properly then voltage can arc out there as well, but it takes quite a long time for modern caps to degrade to that point so id say a faulty flyback is probably more likely.

For obvious reason, i would strongly advise against using the Blueberry machine any longer in this state. At best it could eventually fry other analogue video output components, and at worst, it could cause a fire. The Dalmation machine I would only use under close supervision if at all, and if the problem develops further, also diacontinue using it until it is rectified.
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