iMac Flyback Transformer

[greyiMac]

Hello all,

I recently re-acquired my 400mhz graphite iMac DV SE from high school.  Talk about some nostalgia.  I replaced the HDD, installed MacOS 9.2.2, and installed a ton of apps and games.  Even set it up as a cool little retro desktop in the living room for my little girl.

Everything was going great until I heard a zapping sound, and now it won't boot up.  No chime, even.  I think the flyback transformer kicked the bucket on me.  Which is really sad, since I just spent so much time getting it set up.  I'm totally bummed out.

Does anyone know what model flyback transformer I could use to replace this thing?  (Yes, I'm aware of the inherent dangers of CRT parts, and would be getting an experienced friend to help out)

[GaryN]

You heard a "zapping sound" and assumed it was the flyback.

While that is certainly possible, I can tell you that from my years of experience servicing CRT video, on a purely percentage basis, it's more likely the the horizontal drive transistor that is the culprit.

So, open it up and:
1) Examine the flyback. If it has an obvious burn or crack, well duh, it will need replacement. But even if it looks/is bad…
2) Test that transistor with a multimeter. Both terminals and the case, all combinations in both directions. You're looking primarily for a dead short, so you may not have to even remove it to test, but do so if the results are at all uncertain.

The transistor or its equivalent can be easily found… the flyback, not so much. It IS possible that both are bad, but if you can't see a crack (even hair-thin) on the flyback the odds are in your favor it's just the transistor.

Don't forget, since you didn't actually see it happen, it's possible that neither of them are bad. It could be something else entirely.

Fun, huh?

[greyiMac]

Thanks for the heads up  and wisdom!   I would definitely be pleased if the bad part is something easier to get my hands on.  I'm looking at the common culprits, and people were posting similar symptoms I had about the flyback.  I did note a few visual screen 'glitches' spaced over long periods before it died.

I'll keep my fingers crossed when I crack it open.  It's been a nerdy blast setting this thing up, but more so when it was actually working...  Cheers!

[Greystash]

I have similar issues with mine. It started arcing a lot so I cleaned it out thoroughly with an air duster, made a big difference. I also noticed that whatever is used to seal the CRT to the tube had broken down/was falling off, I'm not sure how much this plays into things..
After running for a while with no arcing it abruptly powered off and wouldn't power back on for a few hours. After that I have stopped using it altogether, there seems to be no CRT repairers in my city and I don't want to dabble with any high voltage components. Good luck with yours!

[IIO]

i once learned the 24 hours rule. how to be sure when you are allowed to open a CRT: unplug, wait 24 hours.

[DieHard]

i once learned the 24 hours rule. how to be sure when you are allowed to open a CRT: unplug, wait 24 hours.

Don't be a Bjork and use your fingers !  (she's so hot)
https://www.youtube.com/watch?v=a6FMpvs71pc
OMG... this is how we did it back in the day when we were an "Apple certified repair" company in New York circa 1998,
yes way before the apple store, they actually certified us little guys

That's an "OK" rule if you have a bleeder resistor in the cap, but many CRTs can shock you and I mean a bad shock even after the "24 hour" rule; to be safe use  long screw dirver and dis-charge it; and you don't have to wait at all

https://www.youtube.com/watch?v=0X28FX_XxtU

[FBz]

I'm still not gunna do it.

Bjork or no.

[IIO]

certified and killed by apple.

[refinery]

back when I was in high school, my electronics teacher, who was also the track coach and an ex-marine, would tell his electronics students quite graphically how he peed his pants when he accidentally discharged a CRT tube by touching it. It was an effective message to the class.