Thread
Larger CRTs on Early Compacts
I've vaguely thought about using one of my TRS-80s in a modified capacity. Assuming the interface is visibly identical, can I use larger CRTs on any of the early compacts?
Or you could *not* destroy another antique, but whatever.
[As I mentioned to you in the other post, the Compaq Plus did not work, and is entirely intact albeit disembodied [so the "another" would not apply].]
And unrelated, except to the topic, I'm pretty sure this specific thought will work. http://www.classic-computers.org.nz/blog/images/2012-07-03-inside-model1-monitor.jpg(although this is a Model I)
And unrelated, except to the topic, I'm pretty sure this specific thought will work. http://www.classic-computers.org.nz/blog/images/2012-07-03-inside-model1-monitor.jpg(although this is a Model I)
Anything is possible in theory, if you're willing to throw enough time, money and circuitry at it. But I'm going to make a wild guess at "not easily".
The recipe for the UglyMac and other clues about the place suggest that the video output from a b&w compact is roughly the same as PC-world EGA in terms of timing. One of those, you would want to check for yourself. If you find a nice big monitor that matches timing-wise, you miiiight just get away with a little circuitry in between to make the sync and signal polarity match what the monitor is expecting. But plug and play? Nope.
The recipe for the UglyMac and other clues about the place suggest that the video output from a b&w compact is roughly the same as PC-world EGA in terms of timing. One of those, you would want to check for yourself. If you find a nice big monitor that matches timing-wise, you miiiight just get away with a little circuitry in between to make the sync and signal polarity match what the monitor is expecting. But plug and play? Nope.
If the pins on the CRT itself are identical (I think this is the case with the compact, Lisa, and Apple 12" monochrome CRTs), couldn't you use the compact's own video circuitry to drive the larger tube? The tube doesn't care about timings and signal polarities, does it? I am literally asking, not challenging any statements anyone has made.
raoulduke: Do with your own toys whatever you want. You run the risk of becoming the neighbor kid from Toy Story if you let it get out of hand.
raoulduke: Do with your own toys whatever you want. You run the risk of becoming the neighbor kid from Toy Story if you let it get out of hand.
the pinouts of most Black and White tubes are the same.
But there are two catches here. G1/G2 voltage requirements may be different, so it may not be brought into focus.
Also the High Voltage requirement of a larger CRT will almost certainly be required. So you will have raster blooming, or overall dimness.
Smaller CRTs need anywhere from 8K to 10K volts. Larger CRTs need 12 to 14K.
Color CRTs need around 20 to 26K volts, in order to force the beam through the aperture grid/Shadow mask.
But there are two catches here. G1/G2 voltage requirements may be different, so it may not be brought into focus.
Also the High Voltage requirement of a larger CRT will almost certainly be required. So you will have raster blooming, or overall dimness.
Smaller CRTs need anywhere from 8K to 10K volts. Larger CRTs need 12 to 14K.
Color CRTs need around 20 to 26K volts, in order to force the beam through the aperture grid/Shadow mask.
Well there's increased voltages and a new sweep time which means that even if you get a stable image the voltage will be too low for you to properly see it. You can't just hang a larger tube in a compact mac and expect it to work. Most of the mods to run a larger screen basically took the video signal to the analog board and sent it somewhere else in a modified format, often enough it was composite. You will not get high resolutions if that is what you are after unless you use entirely new video circuitry.
When I replaced the broken Samsung CRT with the Clinton green monochrome from my Compaq Plus, which didn't work [Gorgotron...], I replaced the neck (coil) with the original SE/30 neck. Just using the SE/30 graphics board dealt with any of the pin-out differences and (along with replacing the anode) the flyback transformer/bleeder resistor, since the design on the Compaq was different and involved two anode-leads. I've only turned that config on twice though to avoid burn-in from the high resistance phosphor [...Gorgotron... [yes... I'm familiar with the added accuracy of scrolling up...]].
In this case, I've had all these machines since the late-90s. They are entirely original in their components because I have mostly not used them. My goal was not specifically preservation, but that has been the effect. And on that point, of course, because of the imperative for preserving antiques, I assume all your machines are entirely original - as are the few I consider to be in my collection? You haven't recapped them, choosing functionality over form? Because if you have, it seems that the source of your vitriol is ignorance and not principle.
Why is it ignorance? Per my words above about having these machines for a decade and a half and not using them: I was thinking about entirely removing the innards from one of the TRS-80 all-in-one machines, including the CRT, and replacing it all with a Mac logic board and new - albeit larger - CRT as a sort of ad hoc, ironic, Lisa look-alike. So I wasn't planning on affecting any of the internals [exactly like with the Compaq, although as I said I have twice - for a cumulative 5 minutes - used the CRT with an SE board]. What's with the kid in Toy Story... was he creative? [lol]
In any event, I appreciate the info about voltages. Were I to pursue this, when I have time, that's what I'd look into. My preface about the neck/coil and the controller board speak to the fact that there are very unlikely to be physical [literally in this case visible] incompatibilities - since as someone mentioned, the CRTs themselves are probably visibly uniform in their interfaces. The issue would be whether that uniformity belies differences in voltage or polarity - or some other standard [i'm honestly curious how the graphics board will control for size and resolution, since the onboard (/30 analog board) controls are only vert/horiz but not size]. Were I to do this, I'd likely try to find an expendible logic board and CRT. I don't know if I have any old non-computer CRTs anymore.
In this case, I've had all these machines since the late-90s. They are entirely original in their components because I have mostly not used them. My goal was not specifically preservation, but that has been the effect. And on that point, of course, because of the imperative for preserving antiques, I assume all your machines are entirely original - as are the few I consider to be in my collection? You haven't recapped them, choosing functionality over form? Because if you have, it seems that the source of your vitriol is ignorance and not principle.
Why is it ignorance? Per my words above about having these machines for a decade and a half and not using them: I was thinking about entirely removing the innards from one of the TRS-80 all-in-one machines, including the CRT, and replacing it all with a Mac logic board and new - albeit larger - CRT as a sort of ad hoc, ironic, Lisa look-alike. So I wasn't planning on affecting any of the internals [exactly like with the Compaq, although as I said I have twice - for a cumulative 5 minutes - used the CRT with an SE board]. What's with the kid in Toy Story... was he creative? [lol]
In any event, I appreciate the info about voltages. Were I to pursue this, when I have time, that's what I'd look into. My preface about the neck/coil and the controller board speak to the fact that there are very unlikely to be physical [literally in this case visible] incompatibilities - since as someone mentioned, the CRTs themselves are probably visibly uniform in their interfaces. The issue would be whether that uniformity belies differences in voltage or polarity - or some other standard [i'm honestly curious how the graphics board will control for size and resolution, since the onboard (/30 analog board) controls are only vert/horiz but not size]. Were I to do this, I'd likely try to find an expendible logic board and CRT. I don't know if I have any old non-computer CRTs anymore.
Looks like something's wrong with one of the controller boards related to the CRT on the Model III, ironically. (I fixed it, but I think a component on one of the boards is starting to go.)
And anything of that age, thats likely to happen.
Would be nice if you traced it down, and fixed her up!
Would be nice if you traced it down, and fixed her up!
That is probably beyond my abilities but there are some tells, maybe. The second time I powered it on the screen didn't come on until I flipped up the drive closing mechanism. The first time I think it didn't start until I pressed break on disk startup (procedure for booting from cassettes).
Otherwise it wobbles a bit (the screen image), which I think I've read about here regarding old Mac CRTs.
Otherwise it wobbles a bit (the screen image), which I think I've read about here regarding old Mac CRTs.
Bad solder joints.
I'm not going near it with solder.
I'm a purist when it comes to keeping these machines alive. The Model IV works great. Now to try to make boot disks.
Also to return to point, unless one of these died it would probably be too much effort to adapt for Mac novelties.
I'm a purist when it comes to keeping these machines alive. The Model IV works great. Now to try to make boot disks.
Also to return to point, unless one of these died it would probably be too much effort to adapt for Mac novelties.
Oh, dear. Your rapier-sharp wit hath cut me to the quick. Good show, old man!
So... after a stream-of-consciousness rant in which you lay out a case for destroying an antique computer (on the basis that it's not "worth enough" financially for you to care about?) for a kicks and giggles case mod and accuse me (with no basis whatsoever) of being "ignorantly" against things like recapping or upgrading (IE, *not* destroying*) said antiques you suddenly turn around and say you're "not going near it with solder" (to *repair it*) yet are a "purist for keeping these machines alive"? Whatever dude.
Anyway. These things are your toys and if your chosen modus operandi is going to be to neglect them until they trivially break, at which point they become game for whatever mindless desecration crosses your mind, that's your business; I'm certainly not going to pay you a ransom to *not* gut your Model III. Frankly my only point is, I don't know, if you don't give a damn about TRS-80's maybe it might be nice to post a "for sale" ad on the Vintage Computer Forum or just slap them on eBay and let someone who does appreciate them have them. A III/4 without accessories generally only sells for $50-$150, which just about puts them in the "costs more to ship than they're worth" category, (also mostly true of items like a Mac Plus or most other Beige macs, so far as that goes) so sure, if "Money" is the only reason you can see not to destroy one then I'm sure that's not going to be enough to stop you. Just don't pretend you're somehow better than someone who does care *a little* about the intrinsic historical value of the old doorstops.
I misremembered your name and then - completely refuse[d] to - correct myself. [These have both been Aqua Teen Hunger Force references.]
Clearly the dichotomy you see is destroy/repair, whereas the dichotomy I was asserting was original/modified. I was asserting that modification is a form of destroying. It may also be seen as a form of repair. I suppose it depends whether you privilege the machine's original form [the 'antique' you're referring to] or its functionality. I guess I've been lucky enough mostly not to have to make that choice with my collection so far.
I don't trust myself not to destroy something if I go at it with solder. That was the source of my comment. But I did write that in a confusing way so it would have been impossible not to connect those thoughts [per your excerpt]. Re-soldering, by itself, pushes the boundary of what I'm referring to with modification. But I don't trust myself not to destroy something and there's no guarantee it is a component issue.
[My ransom comment, which I removed because it was petty [i'm not sure if that's what you were referring to], was both to highlight the limited impact of the value of these machines as well as the remote nature of your [spurious] comments. As I pointed out with the Compaq in another topic, and was frankly pretty offended you didn't follow up on after spuriously accusing me of destroying another 'antique' machine, was that a) the machine didn't work, and b ) I didn't destroy anything except for part of a sort of [inside-the-case] outer guard frame for the CRT, which has no specific effect on the outward appearance or functionality [of the non-working machine]. So when you made the same spurious accusation again, I thought it best to point out that I had again been speaking theoretically about removing the internals and using the case [a thought I think I had previously mentioned on that other topic regarding the Compaq case]. That generated my thought about what would happen with larger CRTs in a compact Mac [and that, sort of meshed with the first thought, formed the basis for this thread]. That generated your accusation that I was destroying an antique.
I understand the chain of your inferences. They are not illogical. However, it would seem to me you could move toward clarification before - twice now - spuriously accusing me of attempting to destroy my own personal property - property that I've preserved pretty well for 15 years. I suppose I can understand your offense in this context. It has some logical basis. However, I don't think my right of reply here - however stream of consciousness - is inappropriate since I find the caprice and repetition of your remarks offensive. Just because we can do a thing, it does not necessarily follow that we must... do that thing. [These have both been Star Trek VI references.]]
Whatever dude.
Clearly the dichotomy you see is destroy/repair, whereas the dichotomy I was asserting was original/modified. I was asserting that modification is a form of destroying. It may also be seen as a form of repair. I suppose it depends whether you privilege the machine's original form [the 'antique' you're referring to] or its functionality. I guess I've been lucky enough mostly not to have to make that choice with my collection so far.
I don't trust myself not to destroy something if I go at it with solder. That was the source of my comment. But I did write that in a confusing way so it would have been impossible not to connect those thoughts [per your excerpt]. Re-soldering, by itself, pushes the boundary of what I'm referring to with modification. But I don't trust myself not to destroy something and there's no guarantee it is a component issue.
[My ransom comment, which I removed because it was petty [i'm not sure if that's what you were referring to], was both to highlight the limited impact of the value of these machines as well as the remote nature of your [spurious] comments. As I pointed out with the Compaq in another topic, and was frankly pretty offended you didn't follow up on after spuriously accusing me of destroying another 'antique' machine, was that a) the machine didn't work, and b ) I didn't destroy anything except for part of a sort of [inside-the-case] outer guard frame for the CRT, which has no specific effect on the outward appearance or functionality [of the non-working machine]. So when you made the same spurious accusation again, I thought it best to point out that I had again been speaking theoretically about removing the internals and using the case [a thought I think I had previously mentioned on that other topic regarding the Compaq case]. That generated my thought about what would happen with larger CRTs in a compact Mac [and that, sort of meshed with the first thought, formed the basis for this thread]. That generated your accusation that I was destroying an antique.
I understand the chain of your inferences. They are not illogical. However, it would seem to me you could move toward clarification before - twice now - spuriously accusing me of attempting to destroy my own personal property - property that I've preserved pretty well for 15 years. I suppose I can understand your offense in this context. It has some logical basis. However, I don't think my right of reply here - however stream of consciousness - is inappropriate since I find the caprice and repetition of your remarks offensive. Just because we can do a thing, it does not necessarily follow that we must... do that thing. [These have both been Star Trek VI references.]]
Whatever dude.
No, see, it hurt me dearly because I do in fact look just like the Gorgatron. I think it's glandular.
Mmmmhmmm. Let's say you have an dog with a mangled leg. Your options are: #1: you take the animal to the vet and repair the leg with extensive surgical intervention involving screws, a steel rod, and a plastic hip joint, or #2: you kill the animal and have a taxidermist turn it into a Lassie-shaped beer tap. I think a reasonable person would say that you "repaired" the dog in the first case and "destroyed" it in the second. It may be a perfectly good beer tap but it is indisputably no longer a dog. I'm sure your argument would be in this case a Tandy with Mac guts in it would still be a "computer" but... no. All you're using of the original is the skin and that puts it squarely into "casemod" category. And while case mods can be clever and arguably acceptable if the donor system was really and truly scrap and beyond repair they tend not to go down that well in "vintage" circles.
But if something looks like it *might* plug into something else you're all for just rushing right on in there and see what happens? Honestly I'm glad you haven't been killed yet mucking around with CRTs. They'll happily do it for you if you don't treat them with respect.
I don't understand the attitude that you care for "preserving" these machines but the moment they blow a trivial component they're suddenly dead and prime for thoughtless gutting. The problem with your Model III's power supply is most likely aging capacitors, or possibly an iffy regulator; the power supplies Radio Shack used in them were sort of marginal for the two-disk configuration even when they were new and "screen shrinking" on disk access is a classic symptom. A few minutes replacing some components (after spending a few hours practicing on a scrap board from an old radio or something first) and it'll be as good or better than new... but no, you ain't gonna go there?
(In fact, if you want to learn how to repair digital electronics or otherwise learn computers at a low level you could do way worse than a Model III; computers like the III are among the last built entirely out of generic TTL logic with no proprietary ASICs, meaning it's almost completely repairable using standard electronics parts drawer bits. But, hey, maybe that's not where your interests lie. In which case, again, I'd caution you to stay away from parts like CRT power supplies that are full of analog black magic.)
Yes, it was. (And yes, I saw it.)
So, I'm sorry you took offense at the "another" part of my comment, I guess. Apparently that Compaq was totally asking for it and I stand corrected. Have fun or whatever.
My Model III doesn't have a power supply problem. My Compaq does. Each progressive fuse blew every time I tried to turn the machine on [i have said this several times now]. If the old PC power supply I have in the basement doesn't match, then that's the end of the Compaq for the moment. So for the moment, that case is for a scrapped, and is in fact sitting in shell-form in my basement - but it has a 9" monitor slot.
I haven't touched anything else. It speaks exactly to your repetitive desire to just concoct and defame. How precisely does your constructed scenario [that I have destroyed... anything] speak either to reality or to this thread - which is about whether (or since we're beyond whether in theory) which larger CRTs could be compatible with the old compact Macs.
And keep in mind with regard to your dog analogy... these aren't living things. I'm perhaps not the most empathetic person, but I would heal that dog out of a desire to spare pain, not because I externally desire for them to function properly. TRS-80s don't feel pain. We don't know if they dream.
I don't care that you saw my comment about your remote and exogenous desire to forbid someone from doing something where it carried no cost and burden to you yourself. I removed it so it wouldn't continue to pollute this thread. Congrats on flouting that. If you have anything to add about the voltage/polarity issues of the CRT in the Models III or IV (though not directly relevant), or any other larger CRTs, it'd be much appreciated.
I haven't touched anything else. It speaks exactly to your repetitive desire to just concoct and defame. How precisely does your constructed scenario [that I have destroyed... anything] speak either to reality or to this thread - which is about whether (or since we're beyond whether in theory) which larger CRTs could be compatible with the old compact Macs.
And keep in mind with regard to your dog analogy... these aren't living things. I'm perhaps not the most empathetic person, but I would heal that dog out of a desire to spare pain, not because I externally desire for them to function properly. TRS-80s don't feel pain. We don't know if they dream.
I don't care that you saw my comment about your remote and exogenous desire to forbid someone from doing something where it carried no cost and burden to you yourself. I removed it so it wouldn't continue to pollute this thread. Congrats on flouting that. If you have anything to add about the voltage/polarity issues of the CRT in the Models III or IV (though not directly relevant), or any other larger CRTs, it'd be much appreciated.
You said the screen image is getting wobbly and it's not starting up reliably. That's very likely a power supply problem. (Possibly compounded by aging capacitors in on the monitors' analog board... but hey, I forgot, you have no interest in actually fixing any of these problems.)
Regardless... "Concoct and defame"? "remote and exogenous desire"?
Anyway, if you want something directly relevant beyond what a couple people who know what they're talking about have already contributed I'll attempt to clarify it a bit: Yes, the pinout on the back of the 12" CRT tube itself in a TRS-80 is *probably* the same as the 9" in the Compact Mac, but given what appears to be your tendency to conclude that if the plug fits it should "just work" that's frankly probably a dangerous thing to tell you. After all, you said this:
Do you think picture tubes are somehow "plug and play" and the board will just magically figure out what you've done and adjust everything automagically? Because, no, that's not how it works.
Anyway, if you were to thread the deflection yoke attached to the Mac's analog board onto a 12" CRT, which it may or may not fit depending on the model of each, and power it up you *may* get a dim and out-of-focus picture; as Technight noted the flyback transformer on the Mac's board quite likely won't completely make the larger CRT happy and/or might burn out trying. Further, the Mac's analog board itself is mostly "hard-wired" out of cheapness, IE, it's short on adjustment pots, so even if the analog board does have enough reserve in it to power the larger tube adequately you'll probably have to change out some resistors and other components to get a clear, centered, and properly sized picture. (And obviously the resulting picture will have the same 512x342 resolution that the 9" CRT shows because *that* is dictated by the digital circuitry on the motherboard, which likewise will have no idea whatsoever that you changed something.)
(As for using the "analog board" in the TRS-80 to drive the monitor by connecting it directly to a Mac motherboard that's also pretty much a non-starter for a novice. The TRS-80's monitor runs at NTSC frequencies, IE, about 15khz hsync, verses the 22khz the Mac runs at. It would need substantial work to sync at the faster rate and further the output from a Compact Mac motherboard isn't "normal" TTL video, it's a little "odd"; there was a thread about that a few months ago which boils down to even if you have a Multisync monitor that can sync at the Mac's frequencies you need a small amount of additional circuitry to turn the "raw" drive signals from the Mac into standard h/vsync signals.)
In short, this is an awfully ambitious project for someone who's afraid of soldering irons and only learned recently that the part of a CRT with the wires coming out of it wasn't something you could buy an ala carte replacement for when you let air into it.
Thank you very much for the info. These are details I would look into if I ever decided to go ahead with attempting to adapt a larger screen for a compact Mac. It's not clear to me why these topics can't be informative beyond themselves such that if anyone wanted this information in the future it couldn't be also helpful to them... Since I actually pointed out that the interface is identical, it seems that warning against simply attempting to plug-and-play [which, by the way, as I think techknight - also you I think - pointed out, probably would work - if not well] actually is quite helpful to me and anyone else with the socially irresponsible urge to, in the future, tinker with their personal property.
As for factual issues: The screen image sometimes does not come on. The CRT powers up reliably with the machine (the back of the CRT's neck lights up). That does not sound like a power supply issue to me, but I am not an expert. (I'm also pretty sure that wasn't what techknight was saying about the solder joints.)
As for impugning my usage of language... you have now several times made up details ["concoct"ed...] in an apparent attempt to derogate my character ["defame"]. (As with) Your initial insertion into this topic, because it only concerned an aforementioned concoction, was off-topic and therefore an inappropriate outsider-slight ["exogenous"] in relation to an object (my property) to which you have no direct connection ["remote"]. Excellent use of meme-pictures. But I think these words do mean what I thought they did when I used them. I'm also not clear on why I'd be using Word and hence its thesaurus to type in this web-form...
Honestly, I cannot fathom your self-righteousness. If this were an encounter in person, it would be foundationally and intractably awkward. In practical terms, at best your tone [or a similar tone] might stop unqualified people - as myself - either acquiring the requisite knowledge to maintain these machines or from asking questions before embarking on foolish endeavors that harm them.
I will not comment on this again. Have a nice evening.
As for factual issues: The screen image sometimes does not come on. The CRT powers up reliably with the machine (the back of the CRT's neck lights up). That does not sound like a power supply issue to me, but I am not an expert. (I'm also pretty sure that wasn't what techknight was saying about the solder joints.)
As for impugning my usage of language... you have now several times made up details ["concoct"ed...] in an apparent attempt to derogate my character ["defame"]. (As with) Your initial insertion into this topic, because it only concerned an aforementioned concoction, was off-topic and therefore an inappropriate outsider-slight ["exogenous"] in relation to an object (my property) to which you have no direct connection ["remote"]. Excellent use of meme-pictures. But I think these words do mean what I thought they did when I used them. I'm also not clear on why I'd be using Word and hence its thesaurus to type in this web-form...
Honestly, I cannot fathom your self-righteousness. If this were an encounter in person, it would be foundationally and intractably awkward. In practical terms, at best your tone [or a similar tone] might stop unqualified people - as myself - either acquiring the requisite knowledge to maintain these machines or from asking questions before embarking on foolish endeavors that harm them.
I will not comment on this again. Have a nice evening.
Aaaalrighty
[mod hat]
Everyone needs to take it down a notch in here. Less flame and more tech talk please.
[mod hat]
Everyone needs to take it down a notch in here. Less flame and more tech talk please.
So... do I understand these points correctly?
If, for not-so-far-fetched instance, I had a fully functional Plus logic board and analog board and a gutted Lisa that was basically only case and CRT, could I plug the Plus boards (designed to drive a 9" CRT) into the Lisa's 12" CRT and have a working machine? Do the 9" and 12" CRTs fall into different size categories? If so, how non-trivial would increasing the Voltage output of the Plus AB be?
- Most (many, several, a few?) black and white CRTs have the same pins in the same arrangement at the end of their neck.
- Electronics designed for one particular black and white CRT should be able to drive a same-size or smaller CRT (with the same neck-pins) without issue*.
- Electronics designed for one particular black and white CRT should be able to drive a larger CRT (with the same neck-pins) but may have issues with brightness.
If, for not-so-far-fetched instance, I had a fully functional Plus logic board and analog board and a gutted Lisa that was basically only case and CRT, could I plug the Plus boards (designed to drive a 9" CRT) into the Lisa's 12" CRT and have a working machine? Do the 9" and 12" CRTs fall into different size categories? If so, how non-trivial would increasing the Voltage output of the Plus AB be?
If by "correctly" you mean "in a grossly oversimplified way" then yes, approximately, but there are very likely to be enough exceptions in each category that it's dangerous/stupid/foolhardy to take state those bullet points as rules.
Just for shiznets and giggles I gave Google a search string that netted me a PDF service manual for some random Ball-brand CRT monitors from 1977 on Bitsavers; the same manual covered the 5", 9", and 12" versions of the display, and scanning the manual (which I'll admit that I'm very not qualified to interpret in its entirety) several things stood out:
1: The manual did say that the raw voltage settings in the horizontal output stage for the 9" and 12" tubes were the same while the 5" was different. However:
2: The part numbers and values of a *substantial* number of components is different between all three models, or in some odd cases the 5" and 12" would share one part while the 9" would be unique, which is obviously counter to item #1. Probably most importantly the high voltage transformer is *always* different between the three sizes, but there are resistor and capacitor changes here and there across the circuit. (Another interesting anomaly is the 5" and 12" use the same deflector yoke while the 9" is different.)
Does #2 definitively prove that if you, in this particular case, took the 9" version of this chassis and stuffed a 12" tube in it it'd melt/blow up/be completely unusable? No, so far as I know it might work hunky dory and the company just used different components out of an abundance of caution. Or it might work hunky-dory for a while and then melt. Or it might work, sort of, but be out of focus and impossible to size correctly unless you went through the circuit board and swapped out at least some of the components for the correct value. This is analog shiznet pretty much black-magic to anyone who hasn't been trained in the art of TV repair and don't forget that poking around a live CRT carries the definite risk of putting a few thousand volts across your heart muscle.
Considering the damage computer novices do to machines by confusing, say, PC parallel ports with Mac SCSI ports because they happen to use the same connectors I'd say that it's not-so-borderline irresponsible to encourage a novice to look at the "matching pins" on the back of CRT tube and just "try it", because the possible repercussions are a lot worse than just letting the magic smoke out. If you're genuinely smart enough to know what you're in for and able to ask the right questions of the right people then it might be an interesting experiment for someone to try (IE, putting a compact Mac's analog board onto a Lisa or whatnot's tube... after looking up the datasheets and confirming they're at least mostly compatible, obviously), but if you're not, well, I guess some anonymous voice on the Internet isn't going to change your mind if you're determined to go through with it anyway.
There is really no clear-cut answer to this. the majority of the B&W CRTs have the same pinouts.
But, they are all different in regards to G1, G2, and Anode voltages.
But, they are all different in regards to G1, G2, and Anode voltages.
Ok. Thanks for clearing a few technical things up. Not sure I deserved G's tone of disdain, but I'll accept the knowledge and discard the rest.
That said, I think I'm done with this thread.
That said, I think I'm done with this thread.
If you're thinking of the Poor Man's Greyscale Project, as documented on the Power Colour Classic sub-site over at Applefritter, it's always worth bearing in mind that, though he got it to work, kind of, in the end he found the results unsatisfactory and decided to use an off the shelf 9" VGA monitor, ie, a complete, known-good system of matching CRT, analog board and deflection yoke. It's not that great an example of success to take as inspiration. IIRC, he gave up on trying to get the image aligned and in focus after much struggle.
And that's given an example where he not only swapped over the analog board but the CRT yoke (the high voltage, beam deflecting electromagnetic coils) as well, and where the analog board was able to drive the CRT at all. The first is a pain in the neck (pardon the pun), the second isn't in any sense a given between two different monitors.
And those are displays from the same manufacturer, where if anything, they would have had an incentive to use a common analog board and common components if possible, to save money. The fact that they didn't strongly suggests it's not in fact possible, or at the very least feasible.
Gotta agree. One of the things I learned - right here in fact, a few years back - by brainfarting some of my own hack ideas, was that there's a certain level where the questions I need to ask indicate that I probably don't know enough to even try the hack. Now, stuff at logic level and under 12V DC isn't going to kill anyone, but CRTs? Imma do a heck of a lot more reading before I start messing with those things.
But these discussions are still worth having IMO, because at least they winnow out the feasible hacks from the unfeasible ones I shouldn't probably waste any time, money or gear on, at least not yet.
In that spirit, [mod hat] I would ask once again for everyone here *coughGorgonops* to exercise a tad less snark please and thankyou.
Heck, I exploded a PC handheld document scanner thing once by plugging it into a Mac ADB port, and there's only four pins and 5V at play there.
Roger, and I do apologize. My impatience with the "summary as presented" was simply due to, well... and please don't take the personally MinerAl, is that the entire thought-process behind it is wrongheaded, IE, it's applying "tinkertoy" logic to analog electronics and dangerous "here there be dragons" ones at that. It's an easy mistake for a novice to make, I've made it myself. (Granted not with anything *electronic* quite so dangerous._
There once was a publishing outfit called the "Howard W. Sams Company", and starting in 1946 they used to make a fair chunk of their living selling little pamphlets called SAMS Photofacts, which contained physical layouts, detailed schematics, parts lists, etc. And a TV repairman would typically have a floor-to-ceiling bookshelf crammed full of them because every single television uses a different pile of black magic to make it work. To just concentrate in the area of discussion here, TV tubes come in all sorts of flavors that have nothing to do with their socket pinout; for example, tubes vary in their "deflection angle". Draw a "V" from the edges of the screen on a TV tube to the front of the electron gun and the angle covered by the "V" is its deflection angle. The general rule is that smaller tubes have smaller angles and larger ones larger because generically speaking bigger tubes are shallower compared to their size than smaller ones, but within a given screen size two different monitors might have different angles. The drive circuitry and yoke itself need different tweaking for different angles, which means getting the geometry right if you swap a different size/angle tube may well call for rebuilding half the analog board. Television tubes also differ in their "flatness", which again, requires systematic changes to the upstream circuitry.
I stumbled across this, the target audience is TV repairmen, and talks about TV/computer monitor scanning systems. The TL;DR digestion is this: the "theory" is generally consistent across different monitors but the devil is seriously in the details, so if you're going to fix a given monitor you're almost certainly going to need the manual.
In short, willy-nilly swapping tubes around is going to net you a monitor that works poorly, if at all, and it's dangerous if you don't know what you're doing. Trying to digest it down to a few bullet points and telling a novice to have at it is a really bad idea. I'm genuinely sorry I seem to be unable to make this point completely nicely. Again, many apologies.
And it should be added, a logic board with VGA-compatible video output, rather than trying to adapt a classic Mac's internal video signals to VGA.
Now on the other hand if you want to try using the existing TRS-80 analog board and matching CRT, and getting a Mac logic board to drive it ... that might just barely be possible, maybe. It's been established around here before that the timing and resolution of compact Macs is close to EGA, and needs just a simple level and sync converter circuit to drive some EGA monitors.
Here's a thread that discusses some of the complexities and gotchas.
If the TRS scans at a similar rate, and has a similar number of lines of vertical resolution (342 lines for the mac), and the same page refresh rate (60Hz) you might be in with a shot. It won't be plug and play by any means, but it would mark it out as possible, with some signal adaption.johnklos said:
Here's a thread that discusses some of the complexities and gotchas.
I'll drop in relevant links and threads as I find them.
https://68kmla.org/forums/index.php?/topic/11043-vga-on-compact-crt/
https://68kmla.org/forums/index.php?/topic/10836-why-the-unusual-frequency/
EvilTim's MacMP3 takes a different approach: forcing a video card in Linux to match up to a non-standard monitor's resolution and scan rates (plus an added signal matching circuit). That isn't something you will be able to do with a Mac logic board, but it might be an alternative use for your TRS.
The article also has a bunch of useful information.
http://members.optusnet.com.au/eviltim/macmp3/macmp3.htm
https://68kmla.org/forums/index.php?/topic/11043-vga-on-compact-crt/
https://68kmla.org/forums/index.php?/topic/10836-why-the-unusual-frequency/
EvilTim's MacMP3 takes a different approach: forcing a video card in Linux to match up to a non-standard monitor's resolution and scan rates (plus an added signal matching circuit). That isn't something you will be able to do with a Mac logic board, but it might be an alternative use for your TRS.
The article also has a bunch of useful information.
http://members.optusnet.com.au/eviltim/macmp3/macmp3.htm
As I noted earlier, it doesn't. The monitors are essentially NTSC. (15.whatever khz.) When used in the Model 4 the monitor is tuned peculiarly so what would usually be the overscan area is crammed down to be visible on the screen (because the 4 uses 240 of the theoretical 252 available non-interlaced lines vs. the more typical 192 the III does, which is why III software looks a little "squished" when run on a 4), but, yeah, nowhere close to Mac resolution/refresh rates. You would need to find the service manual for the actual monitor parts *used in a particular Model III/4* to determine the likelyhood of success for making the analog board accept a higher refresh rate. And on that topic:
The Tandy manuals for those machines pretty much takes a "here there be dragons" approach to the CRT section, and a "SAMS CompuFacts" manual that's floating around states that several different models of monitor were used over the production lifetime of the machines and references some RCA part numbers that a simple Google failed to find anything useful on. (I find some irony that the SAMS Compufacts manual references *another* SAMS manual for part of the computer it allegedly covers, but I suppose that could be taken as a tacit acknowledgement that a technician skilled in digital circuitry might not be up for repairing a TV.) The III's manual does have a schematic for the monitor used when the manual was printed in 1980 but information beyond that is limited to "turn these knobs to make the screen look right". So... basically, unless you're smart enough to look at a TV schematic and understand it well enough to know what parts you need to change you're probably way over your head.