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View Full Version : Laptop only has CGA out. What are my alternatives for an external display?



Load"*",8,1
April 21st, 2014, 07:48 AM
I recently had the good fortune to move into a larger home, which means that at long last I can set up my collection of vintage PCs.

Among these is an Epson Equity LT laptop. It's the original model, running at either 4.7 or 10 MHz, which means that it only outputs video to the LCD screen or to a connected CGA monitor. (If I had the LT-268 or 286e, it would be possible to add a VGA card, but sadly the original LT has proprietary expansion slots rather than standard ISA slots. The proprietary slots, I'm given to understand, are pin-identical to ISA slots... but they're smaller, so there's no fitting an expansion card into the machine. It only takes the two expansions meant for it, the hard disk and the modem.)

Now, I have one CGA monitor (a Tandy CM5; I used to have an IBM PC color monitor as well, but got rid of it because the screen was badly burned-in with text and there's really no fixing that). It works with the LT, but sadly this monitor probably isn't long for our mortal coil. It whines loudly and flickers quite a bit. For that very reason, I just this week installed 8-bit VGA cards in my XT and Tandy 1000SL, so I wouldn't have to deal with a CRT anymore...

Only, the CGA CRT is the only color display I have that I can hook up to this LT laptop.

So, what I want to know is, do I have any other options here? I have no idea if the LT's onboard CGA is capable of composite video output, for example. (Maybe someone here does. Barring that, does anybody know any way at all to attach a CGA port to any kind of modern display? (Yes, I'm aware that CGA to VGA conversion basically doesn't work because of the whole digital/analog/scan rates thing. What else might there be?)

Stone
April 21st, 2014, 08:06 AM
I have a multisync monitor that will work with any video card, e.g., CGA, EGA or VGA. I use one on the workbench so that I only need one monitor there. If that's of interest, lemme know.

KC9UDX
April 21st, 2014, 08:53 AM
The proprietary slots, I'm given to understand, are pin-identical to ISA slots... but they're smaller, so there's no fitting an expansion card into the machine. It only takes the two expansions meant for it, the hard disk and the modem.)

If I were you, I'd aquire a spare modem and cannibalise it to be a slot adapter. That is, unless the plug is just a card edge connector, in which case building an adapter is even easier.

OT: You do realise your user name is a ?syntax error, don't you? :rolleyes:

RWallmow
April 21st, 2014, 08:56 AM
There's CGA to VGA converters (http://www.ebay.com/bhp/cga-to-vga) out there, I've never played with any of them though, so cant say how good the PQ is. I've tried a few 15Khz NTSC RGB to VGA adapters though, was fairly dissapointed with those though, the CGA ones might or might not be any better, but they are sure a lot cheaper, most seem to be in the $30 area, I would gamble at that price (cost me A LOT more to gamble on 15khz RGB converter).

SpidersWeb
April 21st, 2014, 01:18 PM
If you don't mind spending some cash and really wanted to avoid a CRT, you can get brand new LCD's that do CGA, MDA, EGA etc and have a 9pin plug standard.

There are the converter boxes too, but be wary of models that don't specify they work on an IBM PC, I'm told that many of the cheaper models are designed for arcade machines and there is a slight difference. That'd be ideal if you were using a KVM etc.

You could also take your whining CGA display to an electronics repair agent. Probably just needs the caps replaced. Better to do this now before it actually breaks or you'll risk burning out other components as well. Once the smoke comes out it's not always super easy to put it back in.

vwestlife
April 21st, 2014, 06:59 PM
There's a basic circuit you can make using some resistors and a transistor to convert CGA RGB(I) to monochrome composite. I have the schematic somewhere in my archives. It doesn't give you color, but I've tried it and it does work.

Also it might be worth checking if it already has composite video on pin 7 of the RGB output. I don't know about Epson, but I believe some of the Zenith laptops do that.

Load"*",8,1
April 21st, 2014, 08:24 PM
Also it might be worth checking if it already has composite video on pin 7 of the RGB output.

This sounds like the easiest place to start. Any advice on the simplest way to patch something together and test this? (e.g. Would it work to simply clip and strip one end of an ordinary phono/RCA video cable?)

KC9UDX
April 22nd, 2014, 06:05 AM
This sounds like the easiest place to start. Any advice on the simplest way to patch something together and test this? (e.g. Would it work to simply clip and strip one end of an ordinary phono/RCA video cable?)

It's even easier to stick a paperclip in the hole for pin 7, and touch it to the pin of an RCA patch cable. It's easier yet if you have a couple alligator-clip jumper wires you can use to connect the pin and paperclip, as well as the shield and chassis ground.

wesleyfurr
April 24th, 2014, 07:08 PM
Word doesn't seem to be getting out well...but there is such an adapter out there that works to convert CGA to VGA...just finished building and testing one this evening on my Tandy 1000SL. You'll need a GBS-8220 converter, which does analog CGA to VGA, then pair it up with one of these guys:

http://www.vintage-computer.com/vcforum/showthread.php?40965-Commodore-128-Video-DAC-Board-Available

I haven't tested it really thoroughly, but it did 16 colors beautifully in the Tandy enhanced CGA modes.

Only other thing I've found close is the GBS-8219...but it's $230 and does not support the CGA intensity pin...and for obvious reasons I've not actually tested one.

Wesley