Need some advice on getting a monochrome CGA display to work on an EGA card \ VOGONS

Need some advice on getting a monochrome CGA display to work on an EGA card

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First post, by dada

Posted on 2011-01-23, 15:33

dada Offline

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Hi there,

I was wondering if you could give me some advice. A while back I decided that I wanted to back up some of my old 5.25" floppies from way back when. Since I wasn't sure if it was possible to build in a 5.25" floppy reader in one of my newer computers I opted to search for a cheap second hand computer that had both 5.25" and 3.5" floppy drives so I could move them around to my newer computer.

I managed to find one of those computers for dirt cheap. It came without a monitor, but that wouldn't be a problem since I still had two (confirmed working) monochrome monitors.

So here's what happens when I hook up my old green CGA monitor:

Edit: I'm being told my domain name expired so the image might not be visible. I'm trying to get it back online.

So here's a picture of the video card itself: http://www.yjfy.com/images/oldhard/video/auto_mode_hega.jpg

It has a set of 5 dipswitches on the back but no combination seems to be able to make it work. I tried searching for the card on stason.org but I can't seem to find a card that matches it perfectly (most seem to refer to at least two sets of switches but mine only has one).

So, do you think I could get this to work? Or am I better off buying a card off of eBay that would? Do you have any suggestions for such a card?
Thanks! 😀

Reply 1 of 8, by Old Thrashbarg

Posted on 2011-01-23, 16:08

Old Thrashbarg Offline

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I tried searching for the card on stason.org but I can't seem to find a card that matches it perfectly (most seem to refer to at least two sets of switches but mine only has one).

This seems to be it. Looks like you'll probably want all switches off except switch 3.

If that doesn't work, you could try setting it to the various RGB modes and see if you get any composite video out of either of the RCA jacks... just hook it to a TV or whatever. That'd at least tell you if the card works at all.

Reply 2 of 8, by dada

Posted on 2011-01-23, 17:08

dada Offline

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Old Thrashbarg wrote:
I tried searching for the card on stason.org but I can't seem to find a card that matches it perfectly (most seem to refer to at least two sets of switches but mine only has one).

This seems to be it. Looks like you'll probably want all switches off except switch 3.

If that doesn't work, you could try setting it to the various RGB modes and see if you get any composite video out of either of the RCA jacks... just hook it to a TV or whatever. That'd at least tell you if the card works at all.

Thanks for finding it 😀 Unfortunately only setting 3 doesn't work. I get an image, but it's garbled. I suppose I'll try setting it to an RGB mode and then hooking it up to my TV card to see if I can get an image.

Reply 3 of 8, by Davros

Posted on 2011-01-23, 17:49

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is your monitor actually cga ?

ps: what happens when you hook it up to a lcd (the card has a d-sub ?)

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Reply 4 of 8, by h-a-l-9000

Posted on 2011-01-23, 18:21

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'Monochrome' probably refers to MDA which has ~18KHz (CGA is 16KHz).

If your monitor is really CGA try Standard RGB (On Off Off On). Your monitor has to have a translation cirquit RGB->mono.

1+1=10

Reply 5 of 8, by dada

Posted on 2011-01-23, 19:09

dada Offline

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I'm pretty sure it is a real CGA 😀 I could be wrong! But I've always used CGA mode when using this monitor. It's actually monochrome with green and white. I did try that dipswitch combination (I'm pretty sure I tried all of them sequentially) but it didn't work. Just tried it again and I get no image at all.

Also, I unfortunately don't have another monitor I can test with it, only a d-sub 15 CRT and a DVI LCD. I'll give the composite out a try later tonight though.

Reply 6 of 8, by h-a-l-9000

Posted on 2011-01-23, 19:16

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EGA cards do not produce composite output. These two connectors are dummies that are wired to the feature connector.

Does your monitor have potentiometers on the rear, preferrably one labeled h-hold?

1+1=10

Reply 7 of 8, by dada

Posted on 2011-01-23, 23:02

dada Offline

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h-a-l-9000 wrote:
EGA cards do not produce composite output. These two connectors are dummies that are wired to the feature connector.

Does your monitor have potentiometers on the rear, preferrably one labeled h-hold?

Unfortunately they only change screen geometry, nothing that can be used to fix my problem. 😒

Reply 8 of 8, by dada

Posted on 2011-01-26, 19:49

dada Offline

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Alright, since none of the dipswitch combinations seem to work on either monitor, I'm just going to guess this is either a broken video card or somehow incompatible with my monitors. I'm thinking I should get a different card since I can probably find a good one for cheap on eBay. Like this one for example, would this work?

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