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VGA to MDA Adapter for IBM Monochrome Monitor?

TandyFan

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Joined
Jan 8, 2015
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Location
Massachusetts, United States
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.

Since these are two different display standards, I need an adapter to convert the VGA signal to MDA for viewing on the monitor.

Has anyone done something like this?

Thanks.

(I'm not sure whether "PCs and Clones" is the best sub-forum to post this. I didn't see a sub-forum for monitors.)
 
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Hmmm most people want to go the other direction. I don't know of any pre-made solution to do this.

If your PC has ISA slots, you might consider using an ATI VGA Wonder card (most can output an MDA signal).
 
Hello,

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.

Unfortunately the computer does not have an ISA slot, so using an MDA graphics card is not an option.
 
It's even more awesome when you connect it to a 5150 ;)

Well maybe someone else has an idea.
 
@Tandyfan: Just to make you thinking... MDA means Monochrome Display Adapter. So it can just display two colors: Pixel on, pixel off. Only one color, depending of the cathode ray tube in your 5151 the one color is green, amber, white or blue (only one of them, likely it's green). It even can't display gray scales. But VGA is 256 up to 16 million different colors. What do you expect to see on your 5151 from a color monitor. If you don't know the answer, just install some graphics tool like irfanview (plus plugins) on your modern computer, load one of your digital photos from your camera and convert it to monochrome. Look. Then make a screenshot from your computer and convert to monochrome. Look and think.
 
"Grayscale" can be achieved with PWM.


Also my info about VGA Wonder earlier was incorrect, it can only do CGA and EGA on monochrome monitors.
 
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Based on my understanding, VGA contains red, green, and blue signals that combine at different levels to create those 16 million colors. I am hoping to take one of these colors (red, green, or blue) from the VGA signal and display it on the monochrome monitor.

The VGA output from the computer will display a full screen terminal window with white text and a black background. Since white is composed of all three colors (red, green, and blue), using one of the colors should be enough to produce a green monochrome image on the IBM monitor.

Does this thinking make sense?
 
It may be easier to select one of the monochrome VGA modes instead of trying to transform the colors. Though with the capability of a monochrome monitor, switching to monochrome EGA modes would likely be very simple to adapt. 640x350 slots nicely into a cropped 720x350 field.

*Monochrome VGA is the same as high resolution MCGA which may result in easier searches for information.
 
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?
 
One more thing... MDA monitor is fixed resolution fixed frequency monitor. The specs are:

Type Digital, TTL
Resolution 720h × 350v
H-freq 18.432 kHz
V-freq 50 Hz
Colors 1
Color Intensity 2-4[4]

(Source: Wikipedia)

Now compare to VGA: https://en.wikipedia.org/wiki/Video_Graphics_Array#Technical_details

I don't think that any modern VGA card can support MDA compatible timings., If you send the MDA monitor other timings, it might blow up.
 
So, it isn't possible to change the timings on the graphics card from 31.469 kHz and 59.94 kHz (VGA) to 18.432 kHz and 50 kHz (MDA)?

Is there a way to check whether the graphics card can support these timings?
 
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