Please forgive the lengthly post, but I’m excited to have finally found time to test a GBS-8219 MDA/CGA/
RGB to
VGA converter box, which in theory would allow the use of a standard
VGA monitor with many of the “old school” memory consoles with 9-pin video displays from the late 1980’s to the mid-1990’s such as the
GAM Access, Rosco-ET Eclipse, NSI Melange, and
ETC Vision and Microvision.
The converter cost $155 plus shipping and was obtained from:
http://www.ebay.com/itm/XVGA-box-MDA-RGB-CGA-EGA-to-VGA-industrial-video-Converter-/171238250695
They ship very promptly.
The instruction
manual proved to be somewhat cryptic, so experimentation was necessary. Consoles I tested the
unit with were
GAM Access and NSI Melange which output a MDA signal, and an
ETC Microvsion FX which outputs a CGA-type signal.
First up was trying to get a display on the
VGA monitor from an NSI Melange MDA output.
A cable with a molded DB-9 male on one end and bare
wire on the other was supplied with the converter. A loose DB-9 male and female were also supplied, but without hoods. If you still have a RadioShack, the hood is
stock number 276-1513.
Difficulty getting the MDA to work was encountered with the supplied cable because pins 6 and 7 were tied together inside the molded DB-9 end, which meant that the pin 6
Intensity and pin 7 Video signals were shorted to each other producing an unusable display. Twisting off pin 6 fixed that problem.
The converter itself has an on-screen menu which customizes the
unit. Looking at the attached photos, the important choices are
RGB (A) format, separate H &V sync, 75
ohm impedance, and progressive scanning. In theory pin 7 should carry the video signal, but the converter
manual indicated that pins 6 and 7 were not hooked up inside the converter. By playing with different combinations of connecting the molded
plug’s pin 7 Video
wire to pin 3 (Red), pin 4 (Green), and pin 5 (Blue) of the male DB-9 you’re putting on the bare end, you can create the color text you desire on a black background. I tied the pin 7
wire to pin 4 (Green) for the classic “green
screen” look. See the MDA cable wiring diagram for details.
The same cable worked fine using a
GAM Access
console.
The resulting display is sharp and very usable, but not perfect. Some of the text has slight imperfections, and there is a little what I would
call “jittering” or slight pulsing of certain graphics lines. You can see some of this in the photos. But hey, for a reasonable price I’ve got a nice lightweight
flat panel
monitor for my 25-year old memory consoles!
Getting a display on the
VGA monitor from an
ETC Microvision FX’s CGA-type output was pretty straight forward and the results were similar. See the CGA cable wiring diagram for the details. Have fun!
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