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I have never had an particular interest in EGA or CGA monitors, but (1) every IBM CGA (which is the name of the adapter card) has a composite output, and every CGA monitor I've seen has been a severely lobotomized (as Tony Duell described) TV set. Back in the '70's, I modified a small portable TV set to make a small monitor I could package together with a physically small microcomputer system in a rack-width desktop box about 6" tall. That was the only time I personally did that sort of thing, but everyone I knew to be involved in home computing at the time was able to offer plenty of useful advice on how best to effect this mod, suggesting that it was widely practiced. I have attached many dozens of "EGA" monitors to VGA adapters, and have yet to need to modify the monitor in any way not associated with its sweep rates. This suggests to me that they happily accept the 1V or so analog signal amplitude that the VGA adapter requires. Of course, I normally used the commercially available hardware adapters, consisting of two connectors and cabling ranging in legth between 7' and 1.25", depending on whether it was a cable or just an adapter. I'd suggest that if you have something that works differently and it seems that your schematic does, you may have to proceed differently than I did, but the fact that such a large percentage (100%) of the EGA monitors I've dealt with had no difficulty with the VGA video signals, suggests you'll have no trouble finding EGA monitors that deal with VGA output just fine. I did find some that required a capacitor be changed in order to make the sweep circuit operate at the appropriate rate. At least one case, it required, in fact (this was a NEC Multisync-1) that the vertical hold signal be tweaked (from the knob in the top of the cabinet) when switching from text mode to 1024x768 graphics (Windows) mode. The fact that NEC provided an adapter to go between its monitor and the typical VGA card suggests that this is not an unusual application for their products. Dick ----- Original Message ----- From: "Jeff Hellige" <jhellige(a)earthlink.net> To: <classiccmp(a)classiccmp.org> Sent: Monday, May 07, 2001 3:49 PM Subject: Re: Converting TTL monitor to Analog

Yes, there was. stockholm's NEC monitor on its console is such a monitor. It's a regular SVGA monitor in every sense except for the 9-pin connector -- I have driven it up to 1024x768x256 without difficulty. Definitely not EGA. :-) -- ----------------------------- personal page: http://www.armory.com/~spectre/ -- Cameron Kaiser, Point Loma Nazarene University * ckaiser(a)stockholm.ptloma.edu -- Actually, we can overcome gravity (just not the paperwork involved). -------

I believe that this is Macintosh (DB15) <----> PC (HD15) Peace... Sridhar On 9 May 2001, Iggy Drougge wrote:

The II would do unlimited colors in analog mode and up to 64 colors in TTL mode. It's vertical freq range was 50 - 80 Hz with a maximum resolution of 800 x 560. I believe the 2a was the first to be able to reach 800 x 600, though the upgrade to the GS also was able to. It's horizontal freq. range was 15.5 - 35 khz. Jeff -- Collector of Classic Microcomputers and Video Game Systems: Home of the TRS-80 Model 2000 FAQ File http://www.geocities.com/siliconvalley/lakes/6757

On Wednesday, May 9, 2001, at 01:23 PM, Iggy Drougge wrote: The specs I referenced above are those put out by NEC for that monitor. It's doubtful that the II would do be able to do 800 x 600 in it's vertical freq. range, which is why NEC lists it as a max. resolution of 800 x 560. I believe at that resolution they list it at a vert. freq. of 56 Hz. Even if it could take the vertical freq. low enough to get to 800 x 600 I wouldn't want to have to look at it. 56 Hz will flicker enough as it is. Jeff

XenoSoft skrev: Bah, I spent my entire youth in front of a television watching my Amiga's 50 Hz interlaced signal, through RF! No fancy CVBS or Scart RGB here. Then, when I got a proper monitor, I started running 896?600 at 72 Hz interlaced. =) -- En ligne avec Thor 2.6a. I use OpenBSD 'coz it has a cool blowfish logo. The other BSDs look satanic. - Anonymous Coward

Rumor has it that Richard Erlacher may have mentioned these words: Hogwash, yourself. Altho I usually agree with what you type, I must seriously disagree with you here... local I can *easily* see 56 & 60Hz flicker, and anything below 72Hz can give me a headache. (Interlaced VGA can give me a *monster* headache in under 30 minutes.) 75Hz for me is borderline but usable, and 85Hz & above are my "target zones". (also, the larger the tube, the easier it is to see the flicker -- at least for me - I'm running 75Hz at work on a 19" tube, and I can still see it.) Just because *you* cannot see the flicker, doesn't mean all humans cannot see or be affected by the flicker. Anywho, just thought I'd throw my $0.000002 in... Roger "Merch" Merchberger -- Roger "Merch" Merchberger --- sysadmin, Iceberg Computers Recycling is good, right??? Ok, so I'll recycle an old .sig. If at first you don't succeed, nuclear warhead disarmament should *not* be your first career choice.

Well, you may be onto something, but it was widely accepted back in the '70's that a human couldn't see the flicker in an interlaced TV picture, and they certainly wouldn't see flicker in 60 Hz refresh of a text/graphic display. In a subdued light environment, not toally dark, but somewhat subdued, particularly in the absence of flourescent lighting, I can't see the normal 30 Hz interlace in normal network TV broadcast signal at all. I can, however, ALWAYS, see the interlace in those overlays produced on AMIGA video editing tools (probably the cheap ones, but often used at educational institutions' video production studios.) I'm aware of this only because a friend of mine told me what was used to produce them, and sometimes their credits include details about how the text and graphics were integrated into the video. I'd suggest you try looking at the 60+ Hz monitor that gives you a headache in an environment free from flourescent lighting. You might even try watching it in a subdued-light, but not dark environment, with something pleasant on the screen. I can look at code or schematic diagrams for about 8 -10 hours, after which it gives me a headache. I'm just trying to rule out effects other than the "flicker" that nobody could see back in the '70's. Back then the 30 Hz interlace was what occasionally caused folks to complain. Maybe I've just been "hardened" to that effect by much exposure. The "beat" between the nearly-60 Hz at which many monitors do their vertical retrace, and the considerably-closer-to-60 Hz at which the lights flash can certainly cause ill effects. Maybe there's an advantage to being unable to see this purported flicker. Dick ----- Original Message ----- From: "Roger Merchberger" &lt;zmerch(a)30below.com&gt; To: &lt;classiccmp(a)classiccmp.org&gt; Sent: Thursday, May 10, 2001 9:58 AM Subject: Re: Converting TTL monitor to Analog

--- John Foust &lt;jfoust(a)threedee.com&gt; wrote: Got one. It sort-of works. It was much less than 10% the cost of a "real" flicker-fixer (which contains enough RAM to buffer an entire frame plus circuitry to squirt out contents of said RAM at a higher scan rate). I forget what I paid for it, but it was still too much. -ethan ===== Visit "The Seventh Continent" http://penguincentral.com/penguincentral.html __________________________________________________ Do You Yahoo!? Yahoo! Auctions - buy the things you want at great prices http://auctions.yahoo.com/

At 09:04 AM 5/10/01 -0600, Richard Erlacher wrote: I believe there's a new all-digital interface for flat-panel monitors. - John

What sort of digital interface would such devices use? They'd have to have lots of wires, e.g. 26 or so pairs, if the thing is using 24-bit color. Perish the thought someone would use more color depth than that! It's hard to imagine they'd do that. The number of wires that have to transport high-frequency signal is the reason the analog is still so difficult to surpass. After all, a 26-pair shielded cable with an appropriate connector, made in the US, would immediately become the most costly component in a computer system. I doubt a computer maker would go for that, as the 20" monitor (@~$300-$400) is presently the most costly component. That would essentially make the 20" display and cable more than 2/3 the cost of the computer. Dick ----- Original Message ----- From: "Jeff Hellige" &lt;jhellige(a)earthlink.net&gt; To: &lt;classiccmp(a)classiccmp.org&gt; Sent: Thursday, May 10, 2001 2:29 PM Subject: Re: Converting TTL monitor to Analog

Jeff Hellige skrev: Is it just me who's feeling very nervous about AC power to drive an entire monitor going through the same wire as the video signal? I really wouldn't dare hack my own cables for that kind of interface. -- En ligne avec Thor 2.6a. Georgie beundrade stor?gt sin pappa som med v?ldsamma slag gick l?s p? det stora tr?det. Han badade i svett, och den muskul?sa kroppen bl?nkte i solskenet. Hon ?lskade honom. Lady Georgie, TMS 1983

Tony Duell skrev: And then there were the one which went the other way around and put the entire system PSU in the monitor, such as the Amstrad CPCs, the ABC800 and I think the Compis as well. The VAXstation IIGPX had separate PSUs for the monitor and system unit, but the keyboard and mouse connectors were on a box at the monitor cable. -- En ligne avec Thor 2.6a. [E]xcept in the works of Gunnar Asplund, architect of the Stockholm Exhibition of 1930 and the Stockholm crematorium, Sweden has never contributed much to the revolutionary developments through which modern architecture made its initial impact on the world. J.M. Richards, Modern Architecture

Well, I'm not sure you're entirely wrong here, but the ghosting is probably more a result of poor signal termination than anything else, and the magnitude of the reflection from a full-swing digital signal is much more likely to show up than what you'd get form a 1-volt p-p analog signal. Moreover, since you've got much smaller transitions on the analog video signal, and since you've got an automatic gain control in the monitor to offset the losses, the line losses aren't as much a factor as they'd be without it. Digital signaling was OK back in the text-only and monochrome era, but once things went to full-spectrum color, it was necessary to present them in analog. The EGA had 16 (?) colors (maybe that was 16 shades of each of three colors), which already required some digital=>analog processing at some stage in the process, and, from what I've observed, it had to be on the adapter board, since the signal from there to the monitor was already a small-swing analog signal. Gosting is another problem that's never plagued me in this arena. Normally it can be dealt with by proper termination of the video signal. Some monitors rely on a 150-ohm resistor in the line and only provide that same amount themselves, while other have a 75-ohm to ground/return. To accompany this some adapters have a divider rather than simply a series resistor to the output. It depends on what's in the combination, how well it will work, but I've not been sufficiently bothered by any mismatch to warrant hacking either circuit. Dick ----- Original Message ----- From: "Iggy Drougge" &lt;optimus(a)canit.se&gt; To: "Richard Erlacher" &lt;classiccmp(a)classiccmp.org&gt; Sent: Thursday, May 10, 2001 5:26 PM Subject: Re: Converting TTL monitor to Analog

see below, plz Dick ----- Original Message ----- From: "Chuck McManis" &lt;cmcmanis(a)mcmanis.com&gt; To: &lt;classiccmp(a)classiccmp.org&gt; Sent: Wednesday, May 09, 2001 1:29 PM Subject: Re: Converting TTL monitor to Analog <snip> I've seen no evidence of this. If this were the case, then the fact that many display systems use inexpensive 1000 ppm oscillators would cause enough variation that it would be obvious on those monitors having this feature. Moreover, horizontal phase adjustment and vertical height/horizontal width adjustment would be impractical. Amplifier bandwidth issues are a factor in the practical use range of a given monitor. However, that has nothing to do with whether a monitor is analog or digital in nature. While that's true, it's hard to do.

I agree ... but didn't make the remarks which apparently engendered your comment. Dick ----- Original Message ----- From: "Bob Mason" &lt;knightstalkerbob(a)netscape.net&gt; To: &lt;classiccmp(a)classiccmp.org&gt; Sent: Thursday, May 10, 2001 10:06 AM Subject: Re: Converting TTL monitor to Analog It does not directly change the color, only the INTENSITY of the particular color. Cleanest amp I've ever heard. And yes it's over ten years old (purchased in '81). Chip, full ECS chipset, EZ135, 1084S, big harddrives, 2.2xCD http://webmail.netscape.com/

Lets start with this one: them an I'm completely confused by what you say here. What I meant with my remark that it's difficult to do, is that it's difficult to damage a monitor by driving it "all over the map" as you put it. There are monitors that can be damaged by the absence of an appropriate sync signal. Those are fixed-frequency types, however, and they've mostly been damaged already, or they have a home where they are fed the correct signals. The fact is, this discussion has wandered around without any reference to steer it. I agree, that IF there were such a thing as a digital-input monitor, which may exist, it might take a video signal that's digital in nature. I've said, however, that I've never seen one, and I've had, not hundreds, but, over a hundred monitors here that have all happily produced correct-looking and thoroughly useable displays from a nominally 1v p-p analog signal as is produced by a typical VGA/SVGA or whatever you want to call that adapter. I've had exactly ONE CGA (card) and compatible "color" monitor in house, and, after viewing the display on the essentially new monitor, promptly disposed of it, so I've not examined those. I've had little interest in the EGA types, except in that you can buy them for $5 and tweak them to work with a VGA card. That means that I can spend $5 and a little time and then give them to a charitable organization together with an essentially junk-able computer and subsequently write the computer off. Moreover, some of those that I donated nearly 10 years ago are still serving those organizations. I've given these things to friends for use by their kids, and to folks otherwise unable to afford a computer for use in learning to use a computer. Back in '92 or so, I bought a box of surplus 3-1/2" diskettes and found they were sets of Autocad-v12 diskettes, so I gave a set to a fellow who'd been disabled due to a construction accident, along with a computer with a tweaked EGA monitor on it, and that one's still working. I've just not encountered the problem that is apparently at the center of this TTL-monitor thing. You'd think I'd have bumped into at least one. If somebody has a schematic and manual for one of these "digital" monitors, I'd be interested in looking it over. It makes little sense to put a digital signal where an analog one will work, but this is IBM we're dealing with, right? I've seen monitors with switchable termination resistors that respond quite nonlinearly when the terminations are turned off, but those were monochrome types. Now ... see below, plz. Dick ----- Original Message ----- From: "Chuck McManis" &lt;cmcmanis(a)mcmanis.com&gt; To: &lt;classiccmp(a)classiccmp.org&gt; Sent: Thursday, May 10, 2001 10:29 AM Subject: Re: Converting TTL monitor to Analog This suggests that there are precise "spots" that one has to hit. in order to generate an appropriate display. It also seems to suggest that if one move the right margin of the display, leaving the number of pixels unchanged, but increases the dot-clock, one should see evidence of this effect. Moreover, since this is a fixed characteristic of the front-face of the CRT, altering the vertical or horizontal size should make it apparent as well. many I've just now fiddled with the adjustments on my video card, which allows slight horizontal and moderate vertical frequency alterations to be made in software. I've also done this while fiddling with the vertical and horizontal adjustments. I see no evidence of banding or any other anomalous behavior. I don't doubt any of this, but I have reservations about the purported existence of "digital" monitors outside the monochrome world. No disagreement here. <snip>

Just exactly how does this damage occur? While it's not impossible, multisync types have a PLL that either captures the sync signal and uses it or substitutes its own if it can't acquire. It's own is well within a safe range, however. Moreover, the sync rate has nothing at all to do with the question of whether a monitor's video input is "digital" or not. The current generation flat-panel displays are clearly out of scope for this thread, since we're discussing old technology and the context is the question of whether an EGA/VGA monitor is digital or analog and how one might make it work with an existing VGA-type card with analog outputs. There are flat panel displays that take the DE-15 connection ordinarily intended for CRT displays. Dick ----- Original Message ----- From: "Jeff Hellige" &lt;jhellige(a)earthlink.net&gt; To: &lt;classiccmp(a)classiccmp.org&gt; Sent: Thursday, May 10, 2001 2:35 PM Subject: Re: Converting TTL monitor to Analog

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I am cleaning things out (still) and ran across this softbound book. The outer edges are a bit messy with some parts of the front and back covers and nearby pages deteriorated away at the edge. Looks like it got wet at some point. The pages are all readable though. Anyone want this for $3.00 (weighs about 2.5 pounds) including book rate mailing in the US?

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Tony Duell skrev: Not only NEC, in fact. Eizo used it as well, and a while ago, I found a 1996 VGA monitor which used the same 9-pin input. I wouldn't be surprised if Commodore used it in some of their 19XX series monitors as well. The pinout is available on the HWB site. -- En ligne avec Thor 2.6a. Iggy tipsar: Koppla aldrig en C128-transformator till en A500. ?ven om kontakterna ser likadana ut, ligger sp?nningarna fel.

--- Iggy Drougge &lt;optimus(a)canit.se&gt; wrote: My A3000/1950 combo came with such an adapter (and a 23-pin-to-HD-15 adapter as well). The 9-to-15 pin unit works on other vendors' stuff, too. -ethan ===== Visit "The Seventh Continent" http://penguincentral.com/penguincentral.html __________________________________________________ Do You Yahoo!? Yahoo! Auctions - buy the things you want at great prices http://auctions.yahoo.com/

Jeff Hellige skrev: The 3D (which AFAIK is the last Multisync to sync down to 15KHz) has got the depth selector, so did the II, IIRC. Mind you, watch out for the 2A, it only syncs between 31 and 35 KHz or something like that. The II with roman numerals is the one to go for. -- En ligne avec Thor 2.6a. Guilty as charged. Perl is happily ugly, and happily derivative. --Larry Wall in &lt;1992Aug26.184221.29627(a)netlabs.com&gt;

Iggy Drougge wrote: Yes, the Multisync 2A was PC compatible but would not work on Macs. Whereas, the Multisync II (and regular Multisync) would work on both Macs and PCs. IMO, any vintage collector would go along way to have at least one of these beasts. I have at least three in various states of "working." Being somwhat smallish (13" or IBM 14"), they really don't have a market any longer. But there was a time I used to sell the heck out of them right up until a couple of years ago! Eric P.S. I made a group of Mac 15-pin to Multisync 9-pin cables for a school about 5 years ago. When the computer teacher found out (I told her), that Macs didn't need to have Apple monitors and would work fine with Multisyncs I got the job of making the cables. I'm pretty sure I still have many feet of wire with 9-pin and 15-pin connectors, hoods, etc. lying around someplace.

"TTL" refers to Transistor/Transistor Logic. Low usually .5VDC to zero, high >~4VDC, usually 5VDC. IIRC "ECL" is Emitter Coupled Logic. Don't remember the voltage levels. Bob Mason <snip> -- Bob Mason 2x Amiga 500's, GVP A530 (40mhz 68030/68882, 8meg Fast, SCSI), 1.3/3.1, 2meg Chip, full ECS chipset, EZ135, 1084S, big harddrives, 2.2xCD Gateway Performance 500 Piece 'o Crap, 'ME, 128meg, 20Gig, flatbed. __________________________________________________________________ Get your own FREE, personal Netscape Webmail account today at http://webmail.netscape.com/

If you take a look at the output structure used with ECL, which was quite common at one time for sync along with negative-going video on workstation type monitors having very high bandwidth, you'll see the levels that ECL uses range between -1.75 and -0.9, for 0 and 1, respectively. The supply voltages were Vcc=0.0 Volts, and Vee= -5.2 Volts. Other involved voltages include a Vbb at -1.29 Volts, and Vtt at -2 Volts. The typical logic element consists of a diff-amp buffered with an emitter follower. This is very fast, but doesn't swing very far. The emitter follower can't sink current, so the termination is vital. The inputs to the logic element are typically the base of an npn transistor. If you want a good text on signal integrity, I'd recommend the Motorola MECL System Design Handbook, by the way. It's considered by many to be THE definitive work on signal integrity in high speed systems, though it's been around for over 20 years, and, though we don't use ECL as much as was once the practice, the signal integrity issues remain the same. Now that logic swing is gradually approaching the range used with ECL, it seems the work presented is becoming more rather than less relevant. The signal integrity analysis software used by Mentor and by Cadence is based on the work presented in this document and it's still available. Dick ----- Original Message ----- From: "Bill Pechter" &lt;pechter(a)bg-tc-ppp1580.monmouth.com&gt; To: &lt;classiccmp(a)classiccmp.org&gt; Sent: Wednesday, May 09, 2001 7:23 AM Subject: Re: Converting TTL monitor to Analog

Tony Duell skrev: [Very nice explanations regarding the definitions of TTL and ECL snipped] Or the Atari TTM194. BTW, we're having a little problem interfacing an Amiga to a Telenova monitor (a funny beast, it's got a 15 KHz digital input and a 35 KHz analogue one). The Amiga video port features both analogue and digital outputs, but the digital ones are only RGBI (One bit for each colour plus an intensity bit), yielding (according to Tony) only 16 colours, while the Amiga (in this case an A2000) may output as many as 64 colours. This makes palette settings quite adventurous, and games get an entirely different look. How would you go about generating double digital RGB signals and a full set of 64 colours? -- En ligne avec Thor 2.6a. A bore is a man who deprives you of solitude without providing you with company.

Lawrence Walker wrote: NEC Multisyncs have the TTL/Analog switch. Eric