[Coco] GBS-8200 RGB to VGA

[George Ramsower]

  Well, I was convinced that the correct polarity would make it 
work...nope. So, I put a charge pump on it to boost the signal more 
negative....nope.
  This means that I too, am stumped.

  Gene Heskett got one to work but he's busy right now and I'm waiting 
to hear back from him on how he got his to work. It's been a while ago 
and he doesn't use it any longer. He may not remember. I'll keep my 
fingers crossed.
  Meanwhile, it does work with the composite video into the H line on 
that board but it jitters in the 80 Column mode. In OS9, I switch to 
Montype M and the jitter goes away. This implies the color burst is 
messing with that converter. That doesn't really bother me because I 
only use white on black. I really would like the darned thing to work as 
it should.

George R.

On 9/3/2015 1:46 AM, Barry Nelson wrote:
> I have had problems feeding that sync signal to anything except a CM8, even after fixing the polarity and boosting the signal. For some reason the sync on the NTSC video works better. Anyway, try the 7402 and let me know if it works for this.
>
> On Sep 3, 2015, at 1:18 AM, coco-request at maltedmedia.com wrote:
>
>> Date: Wed, 2 Sep 2015 21:53:54 -0500
>> From: George Ramsower <georgera at gvtc.com>
>> To: coco at maltedmedia.com
>> Subject: Re: [Coco] GBS-8200 RGB to VGA
>> Message-ID: <55E7B642.2070102 at gvtc.com>
>> Content-Type: text/plain; charset=windows-1252; format=flowed
>>
>>   I could have used that many years ago when I was attempting to build a
>> line 21 decoder. I'll even bet it was available then but, I didn't know
>> about it.
>>   For the GBS8200, it isn't necessary. The sync is already available
>> from the RGB port on the Coco but, it's the wrong polarity. A simple
>> 7402 is all that is needed.
>> George R.
>