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

[chadbh74]

   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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