A/B and Flyback issue futureproofing from the other side of the Looking Glass?

[Trash80toHP_Mini]

Let it be known, I have very little in the way of knowledge and no competency whatsoever to have a go at this at all, but what I do usually have I'd call a wicked, and truly twisted viewpoint that may or may not have merit in this instance.

I'm surveying the floor of the arena and it seems we've all been looking up at the cliff of the Compact A/B series (CC and AIOs) from the viewpoint of getting more out of the finely tuned pittance available from Apple's designs. Lets twist that around to a top down view of the systems which we know will be failing and have a look from the top of that heap to survey the slope to see what may be accomplished?

I'll bid on the starting point of something of which there may be no living example, the Flyback of the 17" Studio Display's CRT. That's utter insanity from the viewpoint of installing one in the bucket of a 128K, but it is a start. Where can we find a good dividing line? Maybe a 14/15" Trinitron flyback or that of the beloved 12" RGB? I have a sweet spot for that never seen in this life display, it's right atop the pet IIfx sitting next a monstrous 21" Precisionview.

If we can identify the sweet spot spec for the largest, most common, new Flyback salvageable CRT on its way into a death spiral we'll draw a line in the sand to start moving around. Powerful enough to run 5xxx shadow mask or 5xx Trinitron would be a good start maybe?

WAG here is that it will be easy enough to install a crazy spec flyback in a laid back mode on an A/B designed for even a 128K with a few components, achieving a wide range of preset states for spraying the backside of any CRT within its design spec with electrons?

If not, just put me out of my misery right now.

If so, @maceffects are you listening?


edit: thinking that an adapter plate might make one of these things a drop in replacement for some displays?

 

[cheesestraws]

Note that the flyback transformer is part of a resonant circuit which also involves the values of other inductor-adjacent parts in that part of the circuit. AIUI A noticeable change to the properties of the flyback transforemr would require redesign of much of the rest of the circuit also.

 

[Trash80toHP_Mini]

Yep, figurerd out I shouldn't have added that last crazy thought for drop in adapter board after the edit window had closed. Oh well. New PCB projects are poppin' up all over, I think it's high time to graft some analog cuttings back onto the Compact's rootstalk.

Meanwhile, I've been looking at the Flyback of my NIB, unused 10" 1024x768 Color CRT for a while now. Other than being in a spankin' new enclosure, it wouldn't look out of place on my Plus A/B other than being a bit outsize.

Roughly figuring it could drive deflection in a Portrait or 16" Grayscale Display at that resolution? 640x480 should be a walk in the park and anything less in the Compact case would be gravy. Designing resonant circuitry for a small number of preset resolutions using flyback input configurations would be what I'm hoping for here. But as I said, ignorance is bliss at this point. Just shoot me.

Thinking here is that a MultiRes display has a flyback designed for max. res and twiddles inputs for it from the detected video inputs? We need only build a flexible A/B design that can be implemented for any given input. No on the fly changes needed, pick what you want for output from the table, read off and order the components to solder onto the general purpose A/B for flyback I/O?

Implement that witches brew of components for your target resolution, install it, slide the bucket back on and hopefully turn it on without firing it up?

 

[Trash80toHP_Mini]

Tossed visions of this craziness around between my ears bit while caffeinating the wetware this morning. I realized I've got a couple of FlexAB feasibility study candidates right here on hand. Nice thing about it would be that the 12" RGB Pizzabox Lid seems to be fairly plentiful , ships rather well, is frequently available and actual sales pricing levels seem acceptable enough? Its flyback offers some interesting possibilities done on a reasonable scale I'd think?

1 - Was hoping it could be easily "borrowed" for research purposes and reinstalled without modification as is, but not quite
_____ clipping one wire to the neck board is required, but it's black so a bit of shrinkwrap for grafting it back into its home's OK?

2 - Nice big rubber cap makes 8" CRT playtime a breeze, far easier to install/remove than OEM connection.

3 - A/B reference design for its Color Neck Board output at 512x384 included.

4 - Dialing input voltages/frequencies back to 512x384 requirements of Compact GS neck board input's non-trivial but doable?

5 - Equalizing same for running Compact CRT at 640x480 via GS neck board should be well within spec for a color flyback?

6 - 1024x768 in GS on 8" spread of phosphors?

7 - It's bit taller than Compact flybacks, but it'll fit nicely.

8 - Footprint's a bit more than OEM A/B Flyback's footprint as well, but won't be all that visible after all.
______ How many of us are insane enough to poke around at a live flyback outside the bucket while it's hot?

8 - Size will visually balance Seasonic PSU bolted up to opposite corner of FlexAB for fashion photoshoot.


Should have put a ruler on it for scale. 1986 630-0102- board's not on same plane so size comparison's way off, but helps a bit I think:




Anybody have a link handy to datasheet for the SE/30 can's transplanted Seasonic PSU?

Feasibility testing will be design for @apm Compact Mac Retina Display. Two target machines would be:
Classic III project's heavily reworked to Classic Logic board form factor of the fantastic LCIII Logic Board recreation by @max1zzz.
SE/30x rework of IIsi logic board for NuBus/PDS expansion and PPC601 upgrade board in @maceffects clear case. Backburnered ATM?

Thoughts?

 

[Trash80toHP_Mini]

1024x768 10" Color CRT flyback was peeking out at me from it's VisiblePlus window after I'd stowed the 12" RGB back away behind the rollout HackStation. It's a bit more onvenient for putting it in approximately the same plane as the 1986 630-0102 A/B flyback for comparison.

I think this one's taller and more burly than the Pizzatopper RGB flyback, but still fits available cubic. That would make sense as it's far higher resolution capable, if on a bit smaller tube? But playtime's over for today so this one is back on the shelf as well.

Guessing the gray (on this one) and white connections to the neck boards are to implement the RGB trinity? Can those two wires be terminated with input lines unimplemented on the A/B for use in a GS system?



Spent some time ransacking the web for pics yesterday, no joy on the Classic II A/B, but these shots of the first rev. work well as an example for what I need..

Solder side . . . tilted at an angle, not parallel to the surface . . .



. . . not really usable as it's aligned along the backside, not the bottom so traces not aligned horizontally/vertically as in great pic below.



If anyone has a Classic II board, a tripod, three drywall screws and a piece of scrap plywood or particleboard handy, we're in business! If getting at the solder side's not a problem I'll spec a setup for documenting it in three shots.

edit: digital camera would be a big help in this as well.

The A/B can be considered as three separate systems (PSU + audio + video).

I've managed to lobotomize the PSU components and hack in a Pico ATX PSU.

@mogs maybe you could help out with markup of the three seperate systems on this Rev.1 board pic? In whatever graphics program, if you could put color coded boxes around sound and PSU components that'll well define the video subsystem components that need implementing for a Hybrid FlexAB design. Given Seasonic PSU infusion and line level stereo sound output systems provided by the two***** bodysnatcher logic board re-designs in progress, there shouldn't be a whole lot left on that board, no?

Again, link to the Seasonic datasheet used for SE/30 drop in the can PSU replacement would be much appreciated.


*****make that four bodysnatchers by including far the less complicated SE and Plus variants of the LCIII board as originally conceived.

Hopefully I can leave this insanity alone for a while, please let me know if I need to let it sink to the bottom of the Hacks tar pit or should keep chipping away at a spec?

 

[bdurbrow]

If we could find the data sheets for the CRTs themselves, we could design a driver board that uses all modern general purpose parts - a microcontroller to generate the requisite waveforms; voltage multipliers to drive the high voltage for the tube itself, etc…

 

[Trash80toHP_Mini]

I saw you mention that. Wouldn't the inputs from the A/B of any given Macintosh setup be enough to work back from? Several of the CRT makes are interchangeable given several Compact's A/B combo. My dream for years has been a solid state flyback replacement.

Have you got links to information on something like that? Sounds good if not period correct.

Don't know enough to dub it a theory, but my working assumption here is that a powerful enough flyback with Both Color and GS capability can be specified and produced. @maceffects explored the possibility of an SE/30 flyback replacement crowdfunding project some time ago.

If we can drive up to 15" Color CRT AIOs all the way down to the 128K with what I'm calling a FlexAB design and new build flyback we'd be good, That covers a LOT of ground where people sink real money, SE/30/ CC, Lisa and the majority of CRT displays extant for just about any brand or platform. Is the Amiga crown still using period CRT displays? Even Apple II NTSC displays and old TTL designs left alive will be dying in droves before the decade is out. Some crossover there as well? Is classic TV collecting a thing?

Futureproofing that menagerie for another 30 years using tech from the 1990+- 10 year window seems a worthy endeavor?

 

[Johnnya101]

Tv collecting is definitely a thing. The more use cases, the better (sale wise). Although there may be differences in the old flybacks (in old tvs) compared to the newer ones. Also there's the color vs black and white differences, if that mattered in a solid state replacement.

Don't forget arcade game collectors too, they are a big crowd.

 

[Trash80toHP_Mini]

Project so far is to play only with the 12" 512x384 RGB 'zaTopper flyback for a start if that's workable.

One size can't fit all, FlexATX is aimed at Compacts, CC and Lisa as it stands. That's a great start, thanks for info on TV collecting, but don't want to get too far off track. Good to know there are other hobbyists who haven't succumbed to the LCD in EVERYTHING plague.

A larger Flyback for 12" 640x480 RGB through 16" GS displays would be great, but have doubts about something like that scaling down for the smaller boxen. I'm still thinking 17" Color is a bridge too far as I said at the beginning.

Waiting to hear what @apm and @mogs have to say. @techknight are you out there to shoot this thing down in flames?

 

[Trash80toHP_Mini]

Finally bit the bullet and researched just now much I don't know. I love nothing better than plumbing the depths of my ignorance, great fun. Something is telling me I'm way off the rails on this one. Was hopeful a reference design and dialing its flyback performance down from there might get us somewhere. Likely not.

I'd still like those pics of the Classic II A/B and your markup @mogs that'll be very helpful in trying to upgrade the Classic II flyback for 512x384 in GS.

I saw a lot of flybacks on aliexpress and ebay, but no links to datasheets found. Heck, most say "replacement for" without giving any spec at all. This one is my fave: 50-95718-1 Apple Original New Flyback Transformer HD 42086

 

[bdurbrow]

Have you got links to information on something like that? Sounds good if not period correct.

No, I don't - hence the question. I'm wondering if the old Sam's Photofact sets might have something in it?

 

[Trash80toHP_Mini]

All I can say is that an EE didn't laugh at me outright when I asked about the possibility of a solid state flyback.

I'm gonna drop this thread into the tar pit with my favorite research find of all:
https://www.monolithicpower.com/en/how-to-design-a-flyback-converter-in-seven-steps

 

[techknight]

Flybacks are part of a tuned-circuit and help sweep the beam across the tube, if they dont match the original circuit they were designed for, it wont work properly.

Flybacks also produce secondary scan supply voltages, which the entire circuit surrounding it is engineered around. So flyback transformers are pretty specific to the chassis they go in.

Can you swap them around? Sure with enough diligence but you may have to re-engineer large parts of the circuit to accommodate.

To replace the flyback with a solid-state solution, or otherwise known as an "HVG" you would need to compensate for the loss of inductance in the original flyback circuit in order for the horizontal sweep to function properly.

Alot of better designed higher end CRT monitors did just this, they used split horizontal sections. the flyback/HV was its own section outside of horizontal sweep.

In a flyback/yoke combo setup like the compact mac, the Flyback is responsible for Center-left of deflection, while the yoke is doing center-right. Or something like that.

 

[Trash80toHP_Mini]

Thanks, tk. I was wondering if one of the Flybacks on aliexpress might be close enough in spec. range to be capable of being tuned down to supply what's needed for the fabulous Compact Retina Display @apm pulled off using the Classic II flyback?

That'd be the a new build FlexAB notion I'm floating. given enough interest, reworked IIsi and LCIII boards fitting the SE/SE/30 might drive demand high enough to for @maceffects have his tooling pulled out of storage for another production run of his fab case?

Other resolutions can wait, but 640x480 would be first out the gate. Anything lower should be "easy" (read non-trivial enough) to implement I'd think.

 

[Johnnya101]

Hope he didn't get the molds recycled or anything...

Just think, most everything to make a new Mac has been made. Got a new case, got a new speaker, new fan, new logic boards being made.. just need the analog board and power supply. That combined with the LCD adapter being worked on would provide a new old Mac.

 

[bdurbrow]

To replace the flyback with a solid-state solution, or otherwise known as an "HVG" you would need to compensate for the loss of inductance in the original flyback circuit in order for the horizontal sweep to function properly.

What I had in mind was to completely replace all of the circuits on the Analog Board - HV drive for the CRT's anode & cathode; sweep, blanking, etc.

What I'm looking for datasheet-wise is something that gives a) the pinouts of the CRT; and b) the voltages and currents required.