[Coco] Quick question re: RGB -> VGA

[Gene Heskett]

On Monday 24 July 2017 02:20:25 Dave Philipsen wrote:

> Has anyone on the list successfully connected a CoCo 3 to a GBS-8200
> converter? This is a cheap Chinese converter you can buy on eBay for
> under 20 bucks. I'm experimenting with one now but with the lack of
> any good documentation I'm having some problems.  From some posts I've
> read in some forums it's starting to look like the GBS-8200 wants
> composite sync when you're working with CGA-frequency signals.
>
> Right now I'm getting a choppy signal that won't stay locked in. I can
> see the sign on message intermittently and the color is right but the
> sync isn't working yet. At first I thought it was sync polarity so I
> cobbled up a little circuit with a couple of 2N2222s to invert the
> sync. The 'scope shows nice inverted signals but the converter still
> doesn't lock to the signal.  I'm guessing the next step should be to
> try using a NOR gate to combine the HS and VS to make it composite.
>
> Dave

I used one for a while Dave, and thats what I had to do, since torn out 
but IIRC I used a nand gate to center the image.  But that was several 
trillion gallons of water under the bridge ago so don't quote me on the 
nand gate.  My gime seems to have a weak blue drive, so it turns out 
Roy's converter worked better.

Cheers, Gene Heskett
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