[Coco] Re: PSA / warning for all RGB2VGA owners

[Zippster]

Oh yes, we have a working prototype, we just have to refine the FPGA
code a bit and we’ll be releasing VGA adapters for American CoCo2s and
F board CoCo1s.

<https://drive.google.com/open?id=0B1sgl615FlGnfmM0MkRKSFBXLXpCZWFhaTBQNmhlQWNuSU5sdlJTUWhjcWRtNjlEZFgxQzA <https://drive.google.com/open?id=0B1sgl615FlGnfmM0MkRKSFBXLXpCZWFhaTBQNmhlQWNuSU5sdlJTUWhjcWRtNjlEZFgxQzA>>

This won’t be an issue with those.

My guess is Luis tied it to ground based on many VGA port schematics
that are out there.  It’s a mistake anyone could make.  And not an issue
if the correct cable is used.

- Ed


> On Oct 18, 2015, at 10:52 AM, chadbh74 <chadbh74 at hotmail.com> wrote:
> 
>   Is the VGA adapter for the CoCo 2 still being persued?  If so im
>   guessing this issue will be avoided in the design.
> 
>   Sent from my Galaxy Tab 4
> 
>   --------- Original Message ---------
>   From: Zippster
>   To: CoCoList for Color Computer Enthusiasts
>   Date: Sat Oct 17 14:56:24 CDT 2015
>   Subject: Re: [Coco] PSA / warning for all RGB2VGA owners
>   Ok, good to know Steve, and I'm glad the monitor seems ok.
>   I don't have plans to do any more of these, but if I were to, I'd
>   certainly correct
>   the issue first. The boards on OSH Park and any permalinks to them
>   should probably
>   be updated too (or a warning added to the build instructions).
>   - Ed
>> On Oct 17, 2015, at 2:36 PM, Steven Hirsch <snhirsch at gmail.com>
>   wrote:
>> 
>> On Thu, 15 Oct 2015, Zippster wrote:
>> 
>>> Pin 9 is used in some display standards (notably DDC1 and DDC2) to
>   provide +5v from the graphics adapter to the display to read an EDID
>   rom with information about the display even when not powered. The
>   standard calls for this rom to be powered by the display when it's on,
>   so there is the potential that this supply could be connected to ground
>   when using the RGB2VGA board with a cable that has a through connection
>   on pin 9.
>> 
>>> Many, if not most VGA cables appear to have no connection on pin 9,
>   presumably for this reason. I would guess (hope) most displays using
>   this feature would also have some kind of current limiting in place for
>   this situation, as pin 9 is shown grounded in so many pinouts.
>> 
>>> I have heard of no issues so far, but to be on the safe side...
>> 
>> Let me be the first to report an issue, then :-). I have an older
>   Hitachi LCD monitor that seemed to work only intermittantly with the
>   rgb2vga adapter. After reading your post, I checked and discovered that
>   the cable I currently had attached to the monitor did indeed have pin 9
>   connected end to end. I dug through my cable box and found a second
>   cable that did not have this connectivity and, lo and behold, I now
>   have a display on it.
>> 
>> I can only surmise that I had such a cable on it at those odd times
>   when it seemed to work.
>> 
>> Hopefully you will float this pin on future board revisions. It
>   didn't appear to hurt the monitor at all, but it did prevent it from
>   operating.
>> 
>> Steve
>> 
>> 
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