Hercules graphics on VGA monitors (mod)

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Re: Hercules graphics on VGA monitors (mod)

Postby Jo22 » 2018-5-14 @ 23:45

Quick update. Just found a picture and some information of the author's monitor..
The Daewoo CMC-1418AD is also known as "CRYSTAL 14S" (made '94) and has a 14" screen.
Judging by the looks, it could be one of these little monochrome cashier monitors..

crystal_24s.gif
Source: *Link*

If that's the case, it's no wonder the schematic works with video on pin2 only.
Anyway, I'm not sure. Some schematics mention RGB inputs, also. What do you think ?
Could that adapter also work with normal VGA monitors or do I have to wire each RGB pin with a resistor for video/intensity ? :confused:
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Re: Hercules graphics on VGA monitors (mod)

Postby dionb » 2018-5-17 @ 14:54

Can't be certain about *any* VGA monitor, but if you only send an image on green and have red and blue at ground, the worst that would normally happen is a green mono picture (assuming the monitor can make sense of the sync timing). SoG isn't relevant here as you have two discrete sync lines. You could just as easily connect to red or blue for - er - red or blue mono picture.
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Re: Hercules graphics on VGA monitors (mod)

Postby Jo22 » 2018-5-18 @ 23:06

Thank you very much, dionb! :)
So chances aren't that bad that the DB-9->DB15 adapter might work.
I'll write back as soon as the 25MHz oscillating crystals do arrive.
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Re: Hercules graphics on VGA monitors (mod)

Postby Jo22 » 2018-5-20 @ 10:36

Update. Sorry for the delay. The 25MHz parts arrived. I'll do a test tomorrow, maybe.

Edit: Pictures added.
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Re: Hercules graphics on VGA monitors (mod)

Postby Jo22 » 2018-5-22 @ 03:11

Update. Just soldered the 25MHz crystals on the Winbond card..
...and got a success! :D It really works. H-Sync 28,3KHz, 76,4 Hz refresh rate.

My Medion CRT seems to handle it without any problems so far!
No glitches in text mode, so far. ^^

Edit: Quick video available at https://youtu.be/bnW8N6TeiPU
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herc_25_msd.jpg
herc_25_osd.jpg
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Re: Hercules graphics on VGA monitors (mod)

Postby dionb » 2018-5-22 @ 08:13

Wow, it does indeed work!

Colour in photographs is always tricky. I would expect it to be green mono, but some screens detect mono and output white instead. These could be either, what is it like iRL?
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Re: Hercules graphics on VGA monitors (mod)

Postby root42 » 2018-5-22 @ 11:12

Awesome result! Back in the day I would never have thought this is possible! Really great! What happens when you hook it up to an LCD with VGA input? My Philips LED LCD screen so far works with any VGA resolution I can throw at it.
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Re: Hercules graphics on VGA monitors (mod)

Postby Kubik » 2018-5-22 @ 12:09

And you know there's an active Hercules/CGA/MDA/EGA to VGA converter? https://sites.google.com/site/tandycoco ... ega-to-vga
But still, a really great idea!
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Re: Hercules graphics on VGA monitors (mod)

Postby Jo22 » 2018-5-22 @ 20:47

Update. Did a few more tests. The other graphics card failed to display a picture @25MHz.
On neither my CRT, nor my NEC LCD, I was able to see anything.
Here's the CRT out of range message again..
- funnily, the frequencies are the same as provided by the Winbond card..

othe_hgc_25mhz.jpg


dionb wrote:Wow, it does indeed work!

Colour in photographs is always tricky. I would expect it to be green mono,
but some screens detect mono and output white instead. These could be either, what is it like iRL?

I wasn't sure if would work or how it would look, either. I'm glad VGA can indeed work with a single RGB channel.
Thanks for the tip, again! :D In real life, the greens look a bit more vivid.

herc_25_msd_moregreen.jpg


root42 wrote:Awesome result! Back in the day I would never have thought this is possible! Really great!
What happens when you hook it up to an LCD with VGA input? My Philips LED LCD screen so far works with any VGA resolution I can throw at it.

Thanks! ^^ I had my doubts, if it would work with my monitors at all. If I hook my NEC MultiSync LCD 1550ME,
I sadfly get an out of range warning.. Also, graphics mode didn't work so far. Perhaps the software expects 50Hz sync, not sure.
Anyway, it works just fine for text adventures, Tetris and so on. Since my PC/XT clone has CGA on-board, this is not THAT bad.
For other people with a dual graphics setup or some ancient machinery, this Hercules (or rather MDA) "hack" is good to know.
https://youtu.be/j1N_sP8MshY

Kubik wrote:And you know there's an active Hercules/CGA/MDA/EGA to VGA converter?
https://sites.google.com/site/tandycoco ... ega-to-vga
But still, a really great idea!

Hi! Thanks for your reply! I'm not sure if you were writing to me or root42, but as far as I'm is concerned, yes I do. :)
However not for very long (just since about two weeks or so), also I don't know how to construct that device. :sweatdrop:
Say, does an universal chip programmer like the TL866/G540 would wo or does the project require an FGA progamming device ?
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Re: Hercules graphics on VGA monitors (mod)

Postby Kubik » 2018-5-23 @ 05:16

The FPGA can be programmed by cheap (2 EUR) programming device. Anyway, nice hack :) I probably wouldn't want to mod my Hercules card as I prefer to keep it intact (to preserve its historical value), but I was always wondering if Hercules can be attached to VGA :)
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Re: Hercules graphics on VGA monitors (mod)

Postby Jo22 » 2018-5-23 @ 07:02

Thanks! The credits go to Peter, who described this mod on his website. It was fun, though, redoing what he did. :D
The modification can be undone easily, by the way. It's just a crystal swap. ;)
In theory, someone could use a tiny relay with two crystals wired to it (+ a diode across the relay's power pins).
So the frequencies could be changed by the simple flip of a switch.

Anyway, I have a look into the converter, too. It looks interesting.
Maybe it could even be be used with a cheap VGA->CVBS converter.
That way, I could use my old green monitor for both Composite-CGA and Hercules. ^^
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