MDA/CGA/EGA to VGA Converter Released!

Discussion about old graphics cards, monitors and video related things.

Re: MDA/CGA/EGA to VGA Converter Released!

Postby keropi » 2018-2-09 @ 21:54

mateusz.viste MDA is fine on dreamblaster's boards, see this shot I made:

Image

I also think colors will be correct with more precise resistor networks, there is no reason for them not to be
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Re: MDA/CGA/EGA to VGA Converter Released!

Postby mateusz.viste » 2018-2-09 @ 22:16

keropi wrote:mateusz.viste MDA is fine on dreamblaster's boards, see this shot I made:


Yes, I did see it - I was just saying that if he'd happen to have a 'failed' unit that still works with MDA, instead of throwing it out I'd happily buy it since I'm not interested in EGA/CGA anyway. I need it only for debugging programs - a dual screen VGA/MDA setup would be extremely helpful when working on etherdfs (tsr), dosmid (full screen app) and many other of my projects.
Last edited by mateusz.viste on 2018-2-09 @ 22:40, edited 1 time in total.
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Re: MDA/CGA/EGA to VGA Converter Released!

Postby keropi » 2018-2-09 @ 22:23

ah OK yes this is a nice idea actually having dual monitors... I think a couple of games also supported that as well!
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Re: MDA/CGA/EGA to VGA Converter Released!

Postby retrocanada76 » 2018-2-10 @ 17:42

dreamblaster wrote:
mateusz.viste wrote:@retrocanada76 - from your website I understand that you are working on a new, improved v2.0, so I will probably wait for that before assembling anything. One humble suggestion I would have: is there any chance that the v2.0 could come in a "MDA only" variant? This would be nice for people (like me) that do not care about EGA/CGA, but are very interested in monochrome MDA/herc, while not being very handy with a soldering iron at the same time... I assume here that a MDA/herc-only version would need less elements (even if only a few resistors and dip switch).


The 2.0 project is already on his site.
I am working on a version that can be factory assembled.
Lessons learned so far : for next prototypes, I will use better tolerance resistor networks, as the colors seem to differ a bit.
A prototype is on its way to retrocanada, for evaluation.
If it all works well, I'll have a small batch machine assembled.


Hey, I use 5% resistors on mine. I don't think this was the problem. Have you noticed that one of the resistor arrays is isolated and the other bussed ?

Can you tell me which resistor networks did you use for the project ?
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Re: MDA/CGA/EGA to VGA Converter Released!

Postby retrocanada76 » 2018-2-10 @ 17:46

isolated: https://www.digikey.ca/products/en?keyw ... 2-102LF-ND

bussed: https://www.digikey.ca/products/en?keyw ... 1-102LF-ND

ok, my tolerance is 2% but the version 1.0 I used regular 5% 1/4w
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Re: MDA/CGA/EGA to VGA Converter Released!

Postby dreamblaster » 2018-2-10 @ 22:06

I use all isolated resistor networks (all the same part).
The first prototypes had 5% tolerance. (also in the packet I sent you).
Now I ordered parts with 1% tolerance.
We'll see if this solves the issue
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Re: MDA/CGA/EGA to VGA Converter Released!

Postby retrocanada76 » 2018-2-10 @ 22:43

can you send me the schematics ?
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Re: MDA/CGA/EGA to VGA Converter Released!

Postby dreamblaster » 2018-2-11 @ 10:51

retrocanada76 wrote:can you send me the schematics ?


yeah of course, see attachment
RN1 to RN6 are the 1k resistor packs.
I initially used 5% packs. Now I ordered 1% replacements.
(the 1k resistors R1,R2, R3 are already 1%)
Attachments
Printing Print Schematic.pdf
(137.66 KiB) Downloaded 22 times
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Re: MDA/CGA/EGA to VGA Converter Released!

Postby retrocanada76 » 2018-2-11 @ 17:59

can you measure the resistance from each color pin ? From keropi pictures the problem seems to be on B3,G3,B3 they seem to be too bright. These pins should be 500 Ohms each.

B3,R3,G3: 500 ohms
B2,R2,G2: 1K
B1,R1,G1: 2K
B0,R0,G0: 4K
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Re: MDA/CGA/EGA to VGA Converter Released!

Postby dreamblaster » 2018-2-11 @ 19:57

on mine it all seems close enough
Clipboard01.jpg
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Re: MDA/CGA/EGA to VGA Converter Released!

Postby retrocanada76 » 2018-2-11 @ 20:47

So it seems right.
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Re: MDA/CGA/EGA to VGA Converter Released!

Postby retrocanada76 » 2018-2-11 @ 20:49

Dreamblaster, did you try another monitor / tv ? just for the sake. If the voltages are correct there is nothing wrong with the unit.

Use the last FW, and show the colorbars using a different monitor/TV.
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Re: MDA/CGA/EGA to VGA Converter Released!

Postby arteq » 2018-2-12 @ 08:01

do you know where I can by the PCB or complete board for MDA/CGA/EGA to VGA ?
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Re: MDA/CGA/EGA to VGA Converter Released!

Postby keropi » 2018-2-12 @ 08:23

retrocanada76 wrote:can you measure the resistance from each color pin ? From keropi pictures the problem seems to be on B3,G3,B3 they seem to be too bright. These pins should be 500 Ohms each.

B3,R3,G3: 500 ohms
B2,R2,G2: 1K
B1,R1,G1: 2K
B0,R0,G0: 4K


All these check out on my board as well.
Tried latest fw and also a completely different lcd screen, did not help. I will try again once I have installed the 1% resistor networks.
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Re: MDA/CGA/EGA to VGA Converter Released!

Postby retrocanada76 » 2018-2-13 @ 05:51

Sorry, It can't be the resistors. It makes no sense! If your values are correct, them there is no need to replace them. Just do a sanity check and make sure they are not shorted. Specially cross-color, like Bx is not shorting any of the Rx, Gx and remaining Bx's.

It would be wise to take a look on the shift level 74LVC245 as well as the voltages sent from your board. What is the EGA card are you using ?

Do you have another EGA card ? What if you jumper it to CGA display ? Does the text color color bar change ?
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Re: MDA/CGA/EGA to VGA Converter Released!

Postby retrocanada76 » 2018-2-13 @ 07:23

It looks like your reds are too bright. I don't see dark red in the gobliins game.
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Re: MDA/CGA/EGA to VGA Converter Released!

Postby keropi » 2018-2-13 @ 07:58

Yes reds are too bright, almost hot red.
I have tested with 4x EGA cards (at least I have a healthy stock now LOL )

Image Image

Image Image

I did see quality differences but the color balance was constant in all 4 cards. I will wait for those 1% networks and solder them again that way I will also eliminate the possibility of a short.
Not sure how I can check the 74LVC245 though soldering looks great on it.
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Re: MDA/CGA/EGA to VGA Converter Released!

Postby retrocanada76 » 2018-2-13 @ 17:02

I am waiting my board from the overseas but it seems the snail mail is coming on top of a sea turtle... :)
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Re: MDA/CGA/EGA to VGA Converter Released!

Postby ibmapc » 2018-2-13 @ 17:10

arteq wrote:do you know where I can by the PCB or complete board for MDA/CGA/EGA to VGA ?


Hello arteq and others here at Vogons. This is my first time posting here. Some of you might recognize my handle from Vintage Computer Forums. I've been a member there since 2010. I've been selling assembled MDA/CGA/EGA TO VGA V2.0 units to VCF members and am currently working on a new batch to sell. They sell for $110 shipped in the US lower 48. If interested, please email me at gregsaling@comcast.net from your PayPal email and I can send you an invoice to get your order rolling.

Greg

PS
I can ship to other countries as well. It just costs a little more.
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Re: MDA/CGA/EGA to VGA Converter Released!

Postby ibmapc » 2018-2-14 @ 05:33

@keropi;
I see you have and ATI EGA Wonder. Would you consider trading for an assembled V2.0 MDA/CGA/EGA to VGA converter?! We each pay our own shipping? What do ya think? Counter Offer?

Greg
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