[Coco] Coco-3 to the GBS-8220 upscaler interfacing (fwd)

[Steven Hirsch]

See URL in original post below


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---------- Forwarded message ----------
Date: Wed, 4 Jun 2014 07:18:28 -0400 (EDT)
From: Steven Hirsch <snhirsch at gmail.com>
Reply-To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com>
Subject: Re: [Coco] Coco-3 to the GBS-8220 upscaler interfacing

On Tue, 3 Jun 2014, Kandur wrote:

> Recently I got nostalgic and bought a Coco-3 on eBay, got it running and 
> trying to run NirtOS-9 on it. I really have to start from scratch, I seem to 
> have forgotten everything I knew about the Coco. At the moment I'm trying to 
> interface my Coco-3 with an LCD VGA monitor, using the GBS-8220 upscaler 
> board. I need to fix the sync somehow, to make the output more stable. I read 
> a post here from Gene, he used a 74LS04 to combine the Coco's HSync and VSync 
> outputs then connected them via 1n914 diodes to a 1800 ohm resistor, and to 
> the S pin of the GBS-8220 board. He wrote:  '(see the schematic)', but I 
> can't see it. (: Any help regarding the Coco-3 to the GBS-8220 board 
> interfacing would be much appreciated.

See: http://www.epanorama.net/circuits/vga2rgbs.html

The second diagram (VGA to RGB+CSYNC) will do the trick.  It's probably 
possible with fewer gates, but this circuit works very well.  Having said that, 
the GBS-8220 board does not yield a very clean display.  Definitely useable, 
but not pretty.



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