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Flyback opinions wanted

dkjones96

Member
Fortunately I don't think most of us use our compacts enough to 'really' worry about wearing out the CRTs. Keep the brightness down and you are good for 5K hours, easy. Might even squeeze 10-15K if you aren't afraid of a little burn-in and don't mind cranking up the brightness a bit later in its life. Eventually the cathode will get too weak to do its job no matter how easy you are on it but that would most likely be beyond the 15K hour mark.

To put that hour number into perspective, an 8-5 M-F schedule all year is ~2K hours. Color CRTs, in general, were expected to last between 20-30K hours so those have TONS of life left in them for the most part.

9" and up the tubes will likely only have aquadag on the outside of the tube. They tended to aluminize the inside on display CRTs and only small oscope tubes ran with only aquadag. Aluminizing removed the need for ion traps on the larger screens.
 

ktkm

Well-known member
I bought a pricy new old stock 157-0042C (I hope!?) flyback yesterday; since I’m in Sweden, everything becomes twice as expensive (shows how desperate I am @maceffects ;)). Anyway, I was poking around the old Artmix site to find more information about the Hyper Power Supply Rev. 4.1 to see if it could be responsible for wearing down the insulation of the flyback faster (it took three years). I even wrote to them about obtaining more information.

https://www.artmix.com/hps_2009_EVO.html
There is a four bullet list at the bottom of this page in Japanese. When translating, one of the bullets reads, “In addition, by using a newly designed flyback transformer with HC specifications”, to what kind of flyback are they referring?
 

trag

Well-known member
I'm not sure if this is what it was referring to, but I think Artmix also used to sell a remanufactured flyback.
 

aeberbach

Well-known member
I would not expect anyone with a functioning Mac to want a CRT. In some ways it's an improvement but go further down that road and you may as well emulate. The idea is to avoid this situation of unobtainable flybacks and CRTs and all the rest.
 

ktkm

Well-known member
Well, the flyback I ordered had the correct specification, and making the switch went without a hitch. It came as part of an old Mac Plus upgrade kit that besides the flyback, contained some capacitors and diodes (nothing spells old computer parts like an OCR and Optima typed box). However, the new flyback lacks the yellowing glue that I have grown so accustomed to; will that become a problem in the future?

Here are some more pictures from the whole ordeal.
KitFlyback-001.jpeg
KitFlyback-002.jpeg
KitFlyback-003.jpeg
OldFlyback-001.jpeg
OldFlyback-003.jpeg
SolderFlyback-001.jpeg
NewFlyback-001.jpeg
 

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  • OldFlyback-002.jpeg
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joshc

Well-known member
Very nice. Not all of them had that glue, especially later ones which I assume were sealed a different way, so I think that's fine. Your SE/30 is looking great!
 

cheesestraws

Well-known member
besides the flyback, contained some capacitors and diodes (nothing spells old computer parts like an OCR and Optima typed box).

Ah, yes, this looks like the old "Apple underspecced the PSU and now it's cooking itself, please don't" upgrade kit
 

trag

Well-known member
Well, the flyback I ordered had the correct specification, and making the switch went without a hitch. It came as part of an old Mac Plus upgrade kit that besides the flyback, contained some capacitors and diodes

Those kits were great back in the day. I bought five of one kit (probably a different brand) in the early/mid 90s and it included all the parts that Larry Pina recommends replacing in a Compact overhaul.

The pricing was wonky. They wanted $50 per kit, but if you bought 5 or more, the price was $25 per kit. So any number greater than 2 and you might as well buy 5.

I think I still have an unopened one in the attic.
 
I suspect that nobody will ever make or repair the CRTs that exist today.

It seems like it should be possible to design a board that connects to the analog board (with flyback removed and maybe replaced with some resistors to stabilize voltages if necessary) and output LVDS for an LCD. I have a sinking feeling that it would involve a raspberry pi where we should be able to get by with several orders of magnitudes fewer transistors and little to no software.

It would also be completely reasonable to design a replacement for the analog board that also drives an LCD. Maybe it would be more work than is necessary. I don't have the chops to do either of these.

In the meantime, as a guy who owns three vacuum pumps, two of them slightly beefy, and knowing a guy who owns a vacuum pump as big as a labrador, I gotta think that maybe we can rehabilitate some of the flyback transformers by immersing them in lacquer and pulling a vacuum on them for a few minutes to replace all of the air gaps with more lacquer.

The flyback in my Plus shows some minor spangle where the original glue has failed if i look at it in the dark, and i am considering pulling it off the board so i can scrub off most of the decomposed glue, slather it with a slow-setting epoxy, and then putting it in a vacuum chamber until the epoxy cures.
 

techknight

Well-known member
I suspect that nobody will ever make or repair the CRTs that exist today.

It seems like it should be possible to design a board that connects to the analog board (with flyback removed and maybe replaced with some resistors to stabilize voltages if necessary) and output LVDS for an LCD. I have a sinking feeling that it would involve a raspberry pi where we should be able to get by with several orders of magnitudes fewer transistors and little to no software.

It would also be completely reasonable to design a replacement for the analog board that also drives an LCD. Maybe it would be more work than is necessary. I don't have the chops to do either of these.

In the meantime, as a guy who owns three vacuum pumps, two of them slightly beefy, and knowing a guy who owns a vacuum pump as big as a labrador, I gotta think that maybe we can rehabilitate some of the flyback transformers by immersing them in lacquer and pulling a vacuum on them for a few minutes to replace all of the air gaps with more lacquer.

The flyback in my Plus shows some minor spangle where the original glue has failed if i look at it in the dark, and i am considering pulling it off the board so i can scrub off most of the decomposed glue, slather it with a slow-setting epoxy, and then putting it in a vacuum chamber until the epoxy cures.

You have to cut out the cracks and check for carbon tracking first, otherwise you are wasting your time. Then once that is clear, you then have to bake the transformer to drive out ALL moisture.

At this point, you dip it in a pot of hot boiling wax and that pot is sealable. once you do this, pull a vacuum on that pot and the wax will work into the unsealed areas. Again boiling wax to drive out any moisture. it should no longer be boiling when you dip it in and pull a vacuum, but still be VERY hot.

At this point, you can probably seal the rest of it with high voltage non-acidic silicone. like corona dope.
 

techknight

Well-known member
Is that how they do it at the factory? Again, I am amazed at how you know all of this...

No, thats just how you repair transformers that have had issues with insulation, sealing and carbon tracking if its not too far gone. This dates back to the olden days with Tube type TV sets that used the wax covered flyback transformers. The result is the same even with modern transformers.

Once the winding shorts, or arcs over, its done. Trick is to get it BEFORE that happens.
 
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