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VGA to MDA Adapter for IBM Monochrome Monitor?

TandyFan said:
Thanks for the information krebizfan. How would I switch to the monochrome VGA mode? It seems unlikely that a newer computer would have such an option.

As for the actual connection from the computer (VGA) to the monitor (MDA), what kind of pinout would be necessary?
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How new a computer is this being tried with? I think monochrome VGA drivers were available through Win 95 and OS/2 Warp; sorry, never really looked at it with even more recent systems. Failure of my monochrome IBM VGA monitor negatively impacted my ability to research the topic. Some drivers should be able to do it. Windows Vista and later expect more capable video as a minimum so aren't good options.

You will need to create an adapter to convert the signals; the more similar the signal the easier the converter should be. I have seen some VGA to Black and White TV adapters which could be a useful starting point. Actually building the adapter is a bit beyond my skill set.
 
TandyFan said:
Yes, I've seen quite a few adapters that convert MDA to VGA (for using a newer monitor with an older computer), but not the other direction./QUOTE]

Can you provide some additional info on such adapters? That would be a handy adapter to have...even though it is opposite of what the OP is looking for... :)

Thanks,

Wesley
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TandyFan said:
I have an IBM 5151 monochrome monitor with a DE-9 connector for MDA. I would like to connect this monitor to a newer computer with a DE-15 connector for VGA.
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The VGA output from the computer will display a full screen terminal window with white text and a black background.
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Does this thinking make sense?
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No, it doesn't. It would be a lot simpler and much less time-consuming to just find a vintage system to connect your vintage monitor to. You can run terminal programs on old PCs; you can even run telnet over ethernet (google "mTCP").
 
TandyFan said:
Hello,

I have an IBM 5151 monochrome monitor with a DE-9 connector for MDA. I would like to connect this monitor to a newer computer with a DE-15 connector for VGA.
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TandyFan said:
Stone,

I am planning to display a full screen terminal window on the IBM monitor, so there will only be text.
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As i understand it VGA has an effective resolution of 720x400 in text mode and MDA has 720×350. Each character in VGA is 9x16, and in MDA it is 8×14. On VGA you can load a custom font and tweak the character size IIRC, so it may be possible to set a VGA card up in a format that is close enough to MDA to avoid requiring a full scan converter.

Some VGA cards can emulate MDA, what this actually outputs to the screen in terms of raster size, i am not sure of. It would appear that sending 720×350 to a VGA monitor would work, but i don't know. I do know that in Linux with custom modlines, and the right VGA card you can get a VGA card to output directly to a TV via the SCART connector (in a graphics mode).

Either way you would still need some external components to do the analogue to digital conversion. The Amdek monitor in the link *may* support standards other than MDA. I used to own a "CGA" monitor that through an adapter could connect to a BBC Master. I don't know how it did this, but i would guess that the adapter exploited some additional functionality of the monitor.

If all you want is text, by far the easiest thing, as already stated, would be to have a PC with an MDA card connected to the monitor running a terminal program. You could have something small footprint like this:

http://www.ebay.com/itm/233-MHz-LEI...351044?hash=item488912b984:g:zI0AAOSwL7VWq-UQ

Not saying i would buy that, as it is very expensive for what it is, and i dont even know it it would work.

If you want graphics, the most practical method I can think of is to get a 486/Pentium system with a Hercules card. I seem to recall a Herc driver for win95, so with this you can output a raster. You could then use something like VNC to connect to a desktop of your choice. I'm sure Linux has options too. Yes it may be a bit slow, but the phosphor on that monitor is very slow anyway.

Andrew
 
Hi, I found an interesting article that talks about exactly what we need, it's from 1989 and from a magazine called Elektor, it talks about an "easy to build" adapter but I'm not so sure about that. Do you know of anyone who has done a circuit like this? I attach the link of the article in Google Drive. Kind regards

drive.google.com

Correos electrónicos DOC-20230322-WA0039..pdf

drive.google.com drive.google.com
 
Patojanet said:
Hi, I found an interesting article that talks about exactly what we need, it's from 1989 and from a magazine called Elektor, it talks about an "easy to build" adapter but I'm not so sure about that. Do you know of anyone who has done a circuit like this? I attach the link of the article in Google Drive. Kind regards
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It’s certainly an interesting circuit, especially the sync separation portion. I might actually have a use for that…

But there’s a couple things to make clear, here: first off, this circuit does no scan conversion. The test case is they’re using it to display output from a PAL BBC micro on a TTL monitor; the difference in line rate between those two standards is about 15% (slower, for PAL) and they run at the same vertical frame rate (50hz), so this is far closer to within specs for the monitor than VGA is, which has a line rate about 80% higher. I doubt many MDA monitors are going to lock onto that. And…

Point #2, the video conversation relies on a single bit brightness cutoff for deciding if a pixel is on or off. This circuit produces *no* shades of gray. So for anything but a DOS prompt it’s likely to be essentially useless.
 
Eudimorphodon said:
But there’s a couple things to make clear, here: first off, this circuit does no scan conversion. The test case is they’re using it to display output from a PAL BBC micro on a TTL monitor; the difference in line rate between those two standards is about 15% (slower, for PAL) and they run at the same vertical frame rate (50hz), so this is far closer to within specs for the monitor than VGA is, which has a line rate about 80% higher. I doubt many MDA monitors are going to lock onto that.
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I think it's not even talking about MDA monitors. 15khz mono TTL monitors were common-ish in the mid 80s, meant to be used with non-PC platforms. This circuit is just separating composite video into video and separate syncs to work with one of those monitors.
 
FishFinger said:
I think it's not even talking about MDA monitors.
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The bold subtitle of the article specifically says “Among the welcome side effects of the current invasion of IBM PCs and Compatibles are the drastic price cuts for high resolution 12 and 14 inch, TTL compatible monochrome monitors.”

It is of note by the second half of the 80’s that MDA monitors that could also emulate CGA weren’t particularly uncommon, so you didn’t necessarily have to take your chances on whether a given MDA-only monitor would happen to sync down to the lower line rate, but considering the machine in the article is a PAL BBC micro I’m not sure a CGA frequency monitor would be happier, given they’re meant for NTSC(ish) framing. (Definitely pick a monitor with vertical size adjustments.)

Maybe ‘generic’ 15kHz TTL monitors were more common in Europe, I dunno, but in the US most computers with them had them in the form of bare chassis units installed internally.
 
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