Can se/30 flyback be replaced by a 157-026C flyback?

Sjuul010 · Jun 25, 2025

I bought a 157-026C flyback, not realizing it is meant for a Macintosh Plus, and thus is an older type than the one that is used in the SE/30.

I have seen the 157-0042C, which is the one that is used for the SE/30, used as a replacement flyback in a Macintosh Plus, but I'm not sure it would work the other way around. Would things go horribly wrong if I use the 157-026C in my SE/30 anyway?

AvadonDragon · Jun 25, 2025

It SHOULD work just fine. The older part could be lacking the bleeder resistor. I don't recall which models included it. Everyone should discharge before working on a CRT anyway. Given the scarcity and cost of flybacks these days using less than ideal parts will probably become the norm.

Sjuul010 · Jun 25, 2025

Yes, I figured this one lacks the bleeding resistor. But like you said, better something than nothing.

JDW · Jun 26, 2025

Wow. Those little guys have gotten nightmarishly expensive:

157-026C Flyback 157026C / Replaces Apple / HR 42031 | eBay

All credit cards are processed with Authorize.net. © 1982-2015 Dalbani. Serving the Electronic Industry Since 1982. Miami, FL 33166. 4225 NW 72nd Ave. Dalbani is a national and international distributor of high quality electronic components and parts.

www.ebay.com

$150

Kai Robinson · Jun 26, 2025

Just a word of warning - I purchased a flyback from Dalbani a few years ago - while it looked new, all the internal windings were melted/shorted together. I never got a refund either.

Sjuul010 · Jun 26, 2025

JDW said:
Wow. Those little guys have gotten nightmarishly expensive:

Yes! I hope it will be worth it.

Sjuul010 · Jun 26, 2025

Kai Robinson said:
Just a word of warning - I purchased a flyback from Dalbani a few years ago - while it looked new, all the internal windings were melted/shorted together. I never got a refund either.

I'm sorry to hear that. Did it damage the machine you installed it in?

Makes me a bit hesitant to swap the thing in right now, since my original one is not completely dead yet.

Kai Robinson · Jun 26, 2025

I never installed it because I checked the winding first.

Sjuul010 · Jun 26, 2025

Kai Robinson said:
I never installed it because I checked the winding first.

Aha. Could you tell me how you did that? I tried using my multimeter to see if all the pins were shorted. I found some were connected one or more others, but I don't know which one should be connected, so I'm not sure what to make of that.

Paolo B · Jun 26, 2025

At page 94 and 95 of Larry Pina’s book “Macintosh Repair and Update Secrets” you will find an overview of the flyback transformer part numbers.
157-026C was originally supplied for Mac Plus. From Mac Plus on, all OEM flyback transformers should have the bleeding resistor, but it is always mandatory to discharge the CRT before proceeding further.
As far as my experience goes, all units designed for monocrome compact Mac’s will do the job.

iantm · Tuesday at 12:42 AM

It seems like dalbani is the only seller on eBay with these. Did you end up salvaging or repairing a donor? Or source it from somewhere else?

Paolo B · Tuesday at 6:32 AM

iantm said:
It seems like dalbani is the only seller on eBay with these. Did you end up salvaging or repairing a donor? Or source it from somewhere else?

Personally, I had a flickering and wobbling SE/30, the image sometimes going dark altogether. I desoldered, dismantled and cleaned it thoroughly, replacing the metal bracket that was keeping the pieces together, which was heavily damaged by oxidation. I also rebuilt the insulation around the collar. Eventuallay, everything worked fine again. However, if the windings are shorted, there’s not much one can do. Should be easy to check, though.

JDW · Tuesday at 6:35 AM

Paolo B said:
I desoldered, dismantled and cleaned it thoroughly, replacing the metal bracket that was keeping the pieces together, which was heavily damaged by oxidation. I also rebuilt the insulation around the collar. Eventuallay, everything worked fine again.

Wow. How, specifically, did you "dismantle" the flyback, and did you shoot photos of that?

Paolo B · Tuesday at 7:32 AM

Not too difficult, indeed. There’s a metal bracket that keeps the three pieces together. There are two small nuts.
In my case, the bracket was very rusty, to the point it was about to fall apart. I replaced it with a spare from a donor.

JDW · Tuesday at 8:02 AM

Ah... The two nuts on bottom...

Well, I've done that sort of removal before, mainly because the brass rod had broken, making it easy to remove after removing the nuts, which you can see below...

Another few photos showing the broken brass rod...

But I never torn that flyback apart further, only because it is sealed and I really don't know how (or if one even should).

Separately from that, about 20 years ago I bought a NOS flyback and had it in its box for years until I swapped it onto another analog board, and that NOS flyback looks like this (rod is not brass)...

Sjuul010 · Tuesday at 8:53 AM

iantm said:
It seems like dalbani is the only seller on eBay with these. Did you end up salvaging or repairing a donor? Or source it from somewhere else?

I ended up never installing it. When I desoldered the original one, I found more troubles on the analog board. Instead I found another se/30 for sale. It was not too expensive and when I opened it I found it had a Daystar P33 accelerator board installed!

Paolo B · Tuesday at 9:05 PM

JDW said:
Ah... The two nuts on bottom...

Well, I've done that sort of removal before, mainly because the brass rod had broken, making it easy to remove after removing the nuts, which you can see below...

Another few photos showing the broken brass rod...

Yes, I had exactly the same issue, just much worse in terms of corrosion of the rod.
The magnetic circuit is an assembly of two pieces which are kept together by the brass (?) rod.
The sealing collar was aged and broken, I rebuilt it with some silicon sealant.
Surely, I don‘t think it’s possible to rebuild the windings.

So, in my case, just cleaning up the whole thing and putting it back together with a spare rod, had been sufficient for addressing the wobbling and unstable picture (redoing all the joints in the process, too, of course).

JDW · Wednesday at 1:10 AM

Paolo B said:
...putting it back together with a spare rod...

Please review the photos in my previous post and closely examine where the metal rod enters the epoxied area of the main body at top. How deep does the rod go into that epoxy? Not sure if I will ever get a spare rod from somebody out there to repair mine like you do, but I just want to prep for that future work by having all the key info from someone experience like you.

And if anyone was a destroyed flyback who wants to donate or sell their "rod", feel free to drop me a PM.

Paolo B · Friday at 8:05 PM

The rod is “U” shaped and symmetric, it is used for obvious assembling reasons.
The epoxy is just a collar, so after removing the two nuts, you could have easily pulled the two u-shaped ferrite elements apart.

JDW · Saturday at 2:59 AM

Paolo B said:
The rod is “U” shaped and symmetric, it is used for obvious assembling reasons.

If the rod is truly used ONLY for structural support reasons, then it shouldn't affect anything electrically if left broken, I wouldn't think. The flyback I had with a broken rod was mounted to the board very solidly prior to my removal of it. Meaning, people with broken flyback rods shouldn't need to worry that screen-related issues they may see are stemming from that broken rod, right?

Can se/30 flyback be replaced by a 157-026C flyback?

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