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Source for flyback transformer?

C

clh333

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Long story made short: After having an SE/30 logic board recapped the jittery-video problem that prompted the recapping in the first place resurfaced. Reading Pina's books I now believe the problem is with the analog board, probably the flyback transformer.

Can anyone recommend a source for a suitable replacement? This hardly seems like the sort of thing you would want to buy on eBay.

Thanks for your replies.

-CH-
 
Based on my experience in recent years, odds are slim to none that you'll find one. When you do, it won't be quite right. I hope for your sake I'm wrong.
 
KC9UDX said:
Based on my experience in recent years, odds are slim to none that you'll find one. When you do, it won't be quite right. I hope for your sake I'm wrong.
Click to expand...

Same here; scoured the web for months trying to find one for an SE/30. All I could find is the very early revisions without the bleeder resistors as used in Mac Plus/512k/128k (which also had quite a few design flaws).

Have you recapped the analogue board and replaced the common transistors/diodes that fail? There are details in Pina's book about it.

I've also had jittery video in an SE due to a bad power supply. The caps in the SE and SE/30 supplies can leak badly; they run pretty hot and the original ratings were marginal at best. I would try these options before the flyback.
 
Jittery video on an early Mac can sometimes be caused by insulation breakdown in the flyback transformer.

Can you hear a hissing sound from the transformer? If you turn the lights off in the room, is there a blue/purple haze around the top of the transformer? Any of these symptoms indicate a bad EHT transformer. If you look closely at the transformer there will probably be lots of tiny cracks in the plastic surface.

There used to be a special silicone sealant for use as high voltage insulation. Sometimes the life of the transformers could be extended by applying this to the surface to seal up the cracks. Beware that ordinary silicone sealant is not suitable and is likely to make the problem worse - you need the special product made for high voltage insulation.
 
Okay, short story made a little longer: The SE/30 is one of several compact Macs that I acquired over a two-year period beginning in early 2017; sequentially the second. Knowing nothing about Macs and less about SE/30s I noticed the jittery video and asked around: the consensus was the caps on the logic board and I sent it out for repair, not trusting myself to perform the work successfully. Needless to say it was tempting to try my own hand but daunting to think of screwing up a relatively rare machine.

So I did the next best thing: I bought another Mac SE to practice on. (I also bought a nice soldering station and some other tools for repair. Yes, this is driving my wife nuts.) Supposedly this Mac was for parts only but it actually ran (no HD, tho). Nonetheless I rebuilt the power supply, I recapped the logic board, I made a CRT discharge tool but didn't have the nerve to risk imploding the CRT** so I stayed away from the analog board.

The point is: I have another analog board that I can swap out, as occurred to me sometime between yesterday's post and this morning. I believe there are only two analog board versions, early and late, in the SE series, so my assumption is that one will replace the other without modification. True?

-CH-

** (Or frying my shorts; I got over it, though later.)
 
Issue has apparently been resolved: On the MLA Compact Mac forum I posted the same question about sourcing the transformer. One of the respondents, Johnnya101, suggested the problem might be due to a poor power supply ground. Taking his advice I loosened and re-tightened both ends of the green wire that runs from the PSU to the chassis. When I reapplied power the display was stable.

Q.E.D. Thanks to all who responded.

-CH-
 
So you're telling us that you had a board recapped and ordered other supplies for a job that was actually a loose wire?

KISS!
 
Going to shotgun "recap" the next one? :)

It could be much worse. I spent weeks poring over a TV trying to find a loose solder joint. Lightly rap the flyback with a plastic screwdriver and the TV would come to life for a while. It had to be a cold joint on the board. But I couldn't find one anywhere. So I gave up and replaced the flyback. An irreplaceable component went up in flames. When it did, the smoke made the cold solder joint on a nearby component stick out like a sore thumb. So now I've got a dead TV that I spent $200 in parts on, plus an incorrect flyback that just looks right.

I'd be inclined to really clean up those grounds and apply some dielectric grease.
 
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I have fixed at least one power supply by randomly hitting a bunch of solder joints on the bottom side of the circuit board. Stupid, but worked great afterwards.
 
Chuck(G) said:
There's also a high-voltage dope available as well as insulating varnish
Click to expand...

Hi,

sorry for the thread necromancy but I recently inspected my Mac Plus' flyback transformer and found that while it's looking in good shape overall, there is a small crack in the plastic on the top, and the sealant on top seems to be dried / cracked too. Can I use the linked chemicals to seal these cracks and hopefully prolong its life? Or is the silicone sealant mentioned by Shred in post #5 something else?

I've uploaded some pictures of the transformer for reference.

Thanks for your advice!

Cheers
mikerofone


Crack is at about 6-7 o'clock on the top case (zoom in).


Looks pretty good from the side.


Lots of cracks in the yellowish goo (zoom in)
 
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