G3 AIO monitor snap.

[Macdrone]

Ok neither case I have does it a lot but its something that when it happens catches you off guard. I am guessing its a flyback issue with a capacitor replacement kind of thing going on, just was wondering since I took the two and made one as decked out as I could. 6mb video ram, AV card, Zip, 768 mb ram, 266 MHz with rev b rom to install os x and have it dual boot.

 

[Schmoburger]

More than likely a failing flyback or failing caps associated with the HV circuit... It's a pretty common type of failure in Mac CRT's from about '97 onwards. The 5xxx Powermacs, and iMac G3's are known for having flyback trouble even when they werent terribly old, and even my 17" graphite Studio Display has been occasionally snapping for a while now... not often, maybe once or twice in a fortnight if that.

From what I'm told bad caps can blow the transformer and when the transformer blows it also invariably takes out a few caps so you kinda have to replace the transformer and associated caps at the same time... I can't verify this however as at this point in time, I havent had a machine that had one fail and was important enough or rare enough to warrant me actually repairing on component level... simply swapped entire A-boards.

I dare say the studio display will be the first one I attempt a repair on when it finally goes for good.

 

[techknight]

These molar macs were known for the snapping even when in service. Back when I was in high school, I was the IT assistant for the school, this was in 2003/2004. Right at the tail-end of these machines service life, and were being replaced by the dell 2400 series black/gray towers in droves. They were hot shit back then.

And the last few remaining were starting to snap. I ended up figuring out that it was 2 different things. on one, it turned out to be the HV regulator caps that keep the high voltage stable were starting to fail and causing the HV to drift way high.

The second one actually was the Focus/G2 block embedded in the flyback that started to fail, and it would intermittently toss 23Kv into the CRT neck focus/screen pins, which are only rated for a KV or two maximum at best.

Then you got the stupid cases where dust/dirt makes it into the anode cap and arcs through it to ground. Then you start to smell corona at that point. What you wanna look for are the spark-gaps on the CRT neck board, when the snap occurs, if you see arcs jump through the sparkgaps on the neck PCB, its because the flyback is shorting on the G2/Focus divider.