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Tandy 2000 Monitor Workaround

M

macdrachma

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Mar 7, 2019
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Hello, all. I have been trying to get a Tandy 2000 back from the dead and have gotten to the point of everything seeming to boot. However, during this time I found out about the weird monitor issues this computer has and that my CM-5 would not work with it. So browsing here I found that older NEC multisync monitors would work.

Well, I have now picked on up along with a DB-9 to VGA adapter and am not getting anything on the screen. (compared to just garbled text on my CM-5.)

Is there some step or piece I am missing to make this work?
 
I may have just got the wrong NEC monitor. I saw that someone had success with the LCD1550 I did not know there was a 1550M and a 1550V. I got the V :hammermon:
 
Do you have the Technical Reference Manual? http://www.classiccmp.org/cini/pdf/Tandy/Tandy 2000 Technical Reference.pdf

The CM-5 (I have one) is a TTL monitor, where VGA is analogue, so an adapter won't do you any good unless the video card outputs an analogue signal (apparently, some PS/2s could use such an adapter with a multi-sync monitor, but that's as far as it goes, I think). I don't have any familiarity with the Tandy 2000 line, but from the pinouts listed in the tech manual, it's TTL output and should work with any CGA/EGA monitor.

The CM-5 is a 200 line monitor, and the monochrome port should output 560x225 (25x80 characters), but given that the monochrome output uses a goofy 8-pin DIN connector rather than 9-pin D-sub, I assume you have the CM-5 connected to the color graphics card? Can you post a picture of the garbled text on the CM-5? Tandy liked to map a block of system RAM to the upper memory for video, so it's possible that it might just have bad RAM.
 
We're confusing multiple things here.

The Tandy 2000 puts out 640x400 resolution at 26.4 kHz, either monochrome with the onboard DIN connector or in 8 colors out of a palette of 16 colors with the optional color video card, originally designed to work with the Tandy CM-1 high-resolution RGB monitor.

The Tandy CM-5 is a 640x200 15.7 kHz CGA monitor, and will not work with the Tandy 2000's video output, even if the connector fits. (Back in the day, multiple incompatible video standards all used the same 9-pin connector -- MDA, CGA, EGA, etc.)

When it comes to using a modern VGA monitor with the Tandy 2000, the main issue is the difference in scan rate -- most VGA monitors are designed to work with a minimum of 31.5 kHz, which the Tandy 2000's 26.4 kHz video is well below. There are some monitors which are capable of displaying a wider range of frequencies, such as older NEC Multisync monitors, but most VGA monitors won't work with it without some kind of scan rate converter. And then, unless the monitor supports TTL (digital) video input, you'd also need a TTL-to-analog converter in order to display all 16 possible colors rather than just 8.
 
vwestlife said:
We're confusing multiple things here.

The Tandy 2000 puts out 640x400 resolution at 26.4 kHz, either monochrome with the onboard DIN connector or in 8 colors out of a palette of 16 colors with the optional color video card, originally designed to work with the Tandy CM-1 high-resolution RGB monitor.

The Tandy CM-5 is a 640x200 15.7 kHz CGA monitor, and will not work with the Tandy 2000's video output, even if the connector fits. (Back in the day, multiple incompatible video standards all used the same 9-pin connector -- MDA, CGA, EGA, etc.)
Click to expand...

Huh. Errors have been made, I was way off! Is the resolution written down in one of the manuals? I was going by the listed text modes, and assumed that because it doesn't use the secondary RGB lines that it should work with a CGA monitor.
I'm aware that not all 9-pin d-sub outputs are compatible. My HX can do a 225 line mode that doesn't work with the CM-5, I need to use my Hewitt Rand EGA-44 for that But the EGA-44 does maximum of 640x350 and can't do 26.4KHz.

Edit** Just looking around, and it seems the NEC Muti-Sync 14" JC-1401P3A could do either TTL or Analog, from 15.75-35KHz ought to work as well with the Tandy 2000. But given the utility, they are NOT cheap! http://legacycomputersnparts.com/ca...d=852&osCsid=d03680ef4365b60fe7874ca31c53d7b0
 
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blackepyon said:
My HX can do a 225 line mode that doesn't work with the CM-5
Click to expand...
Actually the 225-line mode should work fine with the CM-5 monitor. It uses the same video timing as standard CGA (15.75 kHz H, 60 Hz V); it just has less overscan area than 200-line mode, so it might get cut off at the top and bottom when viewed on a TV set or composite monitor.

And Tandy's listed specifications were not always accurate -- they always claimed the CM-5 monitor had a maximum resolution of 320x200, even though all their ads showed it displaying Personal DeskMate, which ran in 640x200 graphics mode! The only real difference between the CM-5 and the nicer, more expensive CM-11 was that the CM-5 had a lower-quality picture tube with a larger dot pitch (more grainy image) and no anti-glare coating.

From the mid-'80s through mid-'90s Sony also had a series of computer monitors which they introduced as a competitor to the NEC MultiSync (Sony called theirs "Multiscan") and were even better than it, with a very nice 0.26 or 0.25 mm dot pitch Trinitron CRT, and the ability to display pretty much any kind of video signal from 15.7 kHz and up. Likewise, Mitsubishi had a series of Diamond Scan monitors with similar capabilities, such as the AUM-1381A.
 
vwestlife said:
Actually the 225-line mode should work fine with the CM-5 monitor. It uses the same video timing as standard CGA (15.75 kHz H, 60 Hz V); it just has less overscan area than 200-line mode, so it might get cut off at the top and bottom when viewed on a TV set or composite monitor.
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First time I tried it when I had just gotten the monitor, it didn't work. Had to use my old monitor to set it to MODE 200. I just tried MODE 225 now, and it worked! What the hell?

Yeah, my Hewitt Rand EGA-44 has a much finer dot pitch (finer shadow mask, because it can do higher resolution)... But a worse squeal than the Tandy CM-5. Not sure if replacing the capacitors would tighten that up or not, but I doubt it. I seem to recall the CM-5 has a dot-pitch of .65mm. Anything with an aperture grill (aka, Trinitron) rather than a shadow mask is worth holding onto.

By the way, I seem to recall that Tandy's 16-colour video despite using the pinout for CGA was due to changing the palette between interlace scans. Is that correct?

I'd have preferred to get a CM-11, but they are more pricey. I got my CM-5 for $20 plus shipping on eBay. Needed a few easy fixes (and a retrobrite when I can get around to it), but not too bad a deal. It's got the Tandy badge, that's all I was worried about. :p
 
blackepyon said:
By the way, I seem to recall that Tandy's 16-colour video despite using the pinout for CGA was due to changing the palette between interlace scans. Is that correct?
Click to expand...
That's a trick one of our VCF members has used to get more than 16 colors out of Tandy CGA, by flickering between different colors fast enough that to the eye they appear to be blended colors:

http://www.vcfed.org/forum/showthread.php?35007-Tandy-1000-TL-85-Color-Demo

But in normal use, Tandy CGA doesn't do anything special like that.
 
vwestlife said:
We're confusing multiple things here.

The Tandy 2000 puts out 640x400 resolution at 26.4 kHz, either monochrome with the onboard DIN connector or in 8 colors out of a palette of 16 colors with the optional color video card, originally designed to work with the Tandy CM-1 high-resolution RGB monitor.

The Tandy CM-5 is a 640x200 15.7 kHz CGA monitor, and will not work with the Tandy 2000's video output, even if the connector fits. (Back in the day, multiple incompatible video standards all used the same 9-pin connector -- MDA, CGA, EGA, etc.)

When it comes to using a modern VGA monitor with the Tandy 2000, the main issue is the difference in scan rate -- most VGA monitors are designed to work with a minimum of 31.5 kHz, which the Tandy 2000's 26.4 kHz video is well below. There are some monitors which are capable of displaying a wider range of frequencies, such as older NEC Multisync monitors, but most VGA monitors won't work with it without some kind of scan rate converter. And then, unless the monitor supports TTL (digital) video input, you'd also need a TTL-to-analog converter in order to display all 16 possible colors rather than just 8.
Click to expand...

I am still struggling with getting my Tandy 2000 to work. I have verified it is working with a garbled output on my CM5, and I got an NEV 1550v for the demo on my YouTube channel, Dinty's Hideaway. I now see what I did wrong, but after consulting a list of monitors which might work, it would appear (ref: http://www.mattowen.co.uk/textfiles...rs-that-support-15-kHz-analog-RGB-signals.htm) that there may not be a commonly available monitor I can use for this system.

I am trying to avoid emulation, so is there anything I can do?
 
Not sure about the NEC LCD-1550V, but the LCD-1550M does work with scan rates down to 15.7 kHz (CGA). If the 1550V does as well, all you'll need to get it to work with a T2000 with the color graphics board is a digital to analog RGB converter. Trixter posted a thread here about which one he recommends.
 
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