[Coco] PSA / warning for all RGB2VGA owners

[K. Pruitt]

Thanks for the head's up, Ed.

My monitor cable has a pin 9.

I didn't want to pull pin 9 from my monitor cable, so I pulled pin 9 from a 
VGA cable extender and put  that between the RGB2VGA and the monitor cable.



----- Original Message ----- 
From: "Zippster" <zippster278 at gmail.com>
To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
Sent: Thursday, October 15, 2015 5:18 PM
Subject: [Coco] PSA / warning for all RGB2VGA owners


> Hi guys,  this is a PSA / warning for all RGB2VGA owners.
>
> It has been brought to my attention by Roger Taylor on the Facebook group
> that the RGB2VGA design has pin 9 of the outgoing VGA connector tied to 
> ground.
> This is the case with both Luis’s original boards, and the SE version (the 
> circuit was
> not changed, just layout and routing).  Many VGA pinouts show this pin as 
> grounded,
> many as no connects, and some as +5V.
>
> 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…
>
> USE THE RGB2VGA ADAPTER ONLY WITH VGA CABLES THAT DO NOT HAVE A CONNECTION 
> ON PIN 9
>
> If there is no cable through-connection on pin 9, then this is not an 
> issue at all.
>
> Thank you,
>
> - Ed
>
>
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