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TandyFan
January 16th, 2016, 11:53 AM
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.)

Plasma
January 16th, 2016, 02:10 PM
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).

TandyFan
January 16th, 2016, 02:23 PM
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.

Plasma
January 16th, 2016, 02:25 PM
Can I ask why you want to use that monitor?

TandyFan
January 16th, 2016, 02:29 PM
I enjoy seeing vintage computing equipment in action, and the IBM 5151 is an awesome vintage monitor.

Plasma
January 16th, 2016, 02:34 PM
It's even more awesome when you connect it to a 5150 ;)

Well maybe someone else has an idea.

TandyFan
January 16th, 2016, 02:35 PM
Yes, I completely agree. Would you happen to have a 5150 to give me? :D

Stone
January 16th, 2016, 04:06 PM
I'll give you one.

But you'll have to pick it up.

1ST1
January 17th, 2016, 08:01 AM
@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.

Plasma
January 17th, 2016, 09:54 AM
"Grayscale" can be achieved with PWM.


https://www.youtube.com/watch?v=pqKGHT-JR1c

Also my info about VGA Wonder earlier was incorrect, it can only do CGA and EGA on monochrome monitors.

TandyFan
January 17th, 2016, 10:06 AM
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?

krebizfan
January 17th, 2016, 10:38 AM
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.

Stone
January 17th, 2016, 10:40 AM
That might work for text but what about the rest? :-)

TandyFan
January 17th, 2016, 10:46 AM
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?

TandyFan
January 17th, 2016, 10:47 AM
Stone,

I am planning to display a full screen terminal window on the IBM monitor, so there will only be text.

Stone
January 17th, 2016, 11:11 AM
I've got a nice paper white (mono) VGA if you want that.

TandyFan
January 17th, 2016, 11:14 AM
Are you referring to a monitor?

I was hoping to put the IBM monitor to use if possible.

1ST1
January 17th, 2016, 11:17 AM
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.

TandyFan
January 17th, 2016, 11:29 AM
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?

Stone
January 17th, 2016, 11:30 AM
Are you referring to a monitor?Is there any other paper white VGA device? :-)

TandyFan
January 17th, 2016, 11:32 AM
I would like to use the IBM monitor rather than a paper white VGA monitor.

krebizfan
January 17th, 2016, 11:52 AM
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?

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
January 17th, 2016, 12:04 PM
I'm not certain which computer will be used with the IBM monitor. I will probably use a ThinkPad laptop (about 10 years old) running the latest version of Ubuntu.

I came across this Reddit post after searching on Google: https://www.reddit.com/r/vintagecomputing/comments/33umve/ibm_mda_monitor_working_on_a_modern_laptop_with/

It seems that someone was able to connect an Amdek monochrome monitor (MDA) to a modern laptop (VGA). The pictures look promising.

Stone
January 17th, 2016, 12:52 PM
I would like to use the IBM monitor rather than a paper white VGA monitor.Yes, I know. There's no challenge there. You just plug it in and it works the first time without any adapter, tuning or adjustment. :-)

wesleyfurr
January 18th, 2016, 05:58 PM
[QUOTE=TandyFan;398288]
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

TandyFan
January 23rd, 2016, 08:24 AM
The "XVGA Box" seems to be a popular converter for replacing MDA monitors with VGA monitors in industrial applications:

http://www.amazon.com/8219-Industrial-Converter-Monitor-Replacement/dp/B00D8W3MSO

I also came across this thread on EEVblog:

http://www.eevblog.com/forum/repair/mda-to-vga-convertor-adapter/

Someone was trying to replace a MDA monitor with a VGA monitor (the opposite of what I am trying to do).

Trixter
January 23rd, 2016, 11:44 AM
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.
...
The VGA output from the computer will display a full screen terminal window with white text and a black background.
...
Does this thinking make sense?

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").

KC9UDX
January 23rd, 2016, 02:49 PM
What is the computer that doesn't have ISA slots?

TandyFan
January 23rd, 2016, 03:21 PM
It isn't a vintage computer. I was planning on using a ThinkPad laptop.

mR_Slug
January 30th, 2016, 07:04 AM
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.




Stone,

I am planning to display a full screen terminal window on the IBM monitor, so there will only be text.


As i understand it VGA has an effective resolution of 720x400 in text mode and MDA has 720350. Each character in VGA is 9x16, and in MDA it is 814. 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 720350 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-LEISER-PC-zB-f-MS-DOS-2x-RS-232-ISA-BUS-LTP-PORT-40GB-HDD-TC200-GRAU40-/311537351044?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