From: Marty Goodman MD KC6YKC <MARTYGOODMAN@DELPHI.COM>
Subject:      RGB pin outs (comment to Mark Haaland)

Just for future reference:

    In figuring out analog RGB pin outs for CoCo or VGA style monitors,
when confronted with a DB 9:

   There are only two really common pin outs used on a DB9 signal
for the standard 5 signals (r,g,b, h sync, v sync) and ground
that comprise separate sync analog RGB signals (the sort of signal
used by the CoCo 3, Atari ST, and VGA based systems).  Indeed,
these two are SO common that I've yet to encounter or even hear of
any other pin out than these two being used on a monitor or
source of video designed to use analog RGB via a DB9 connector.


   These two pinouts are as follows:


 "Sony standard", or you can call this "CGA-like"
    1,2   ground
  3,4,5   r,g,b luminance
     6 NC
     7 comp. sync
     8,9  H and V sync

   This pin out is commonly found on Magnavox analog RGB monitors
    that have DB9's as their video connector.  And of course
    on the Sony monitors that support analog RGB and use DB9's.




  "NEC standard"

   1,2,3  r,g,b luminance
    4,5   H and V sync
   6,7,8,9   all GROUND



   This pin out is also used by Tatung on their mulitsync monitors.
   It's found on all the old NEC multisync monitors that use
   a DB 9 connector, active only when those monitors are in analog mode.
    (when those monitors are in "digital" [CGA or EGA] mode, the
     same connector presents the "Sony" or "CGA" type pin out)


   It's usually easy to figure which of those two pin outs a given monitor
has.   Just use an ohmmeter set to Rx10 scale as a continuity checker
(checking for zero ohms resistance).   Then check for continuity between
the attachment points of the DB9 (the threaded little metal cylinders
that the plug's screws fit into) and pins 1 & 2.   Or even just check
for continuity between pins 1 and 2.   If you find that, you've almost
certainly got a "Sony style" pin out.   If you instead find continuity
between pins 6,7,8 and 9, and continuity between them and the metal
shell / screw holes of the DB9, then you almost certainly are dealing
with a "NEC style" pin out.


   Note that I think the NEC style pin out is the superior design choice,
for when one crimps a piece of ribbon cable to a DB9 connector, if one
is using the NEC pin out, one automatically gets all the signal lines
surrounded on each side by a ground line (except for the edges).  This
makes for a superior transmission of the video signal over ribbon cable,
for its electrical characteristics begin to approximate those of the ideal
case of using separate coaxial cables for each signal.

  ---marty