View Full Version : Yet more RGB questions

November 3rd, 2006, 07:03 PM
As some of you know ("remember" would be a better term for it), I snatched an RGB monitor circa-1987 during neighborhood cleanup. (along with a TRS-80 Model 4)

Today, I managed to salvage what I could of the short stub of the cut cable, & there are the following wires:

-Red (Red)
-Blue (Blue)
-Grey (Green)
-White (I'm assuming Composite Sync?)
-Brown (?)
-Yellow (?)
-Black (Apperantly ground; leads to the same trace as the RGB & cable grounds)

I got RGB & Csync hooked up to my Neo-Geo MVS cabinet, but the image is all blown up.

I've tried putting the Sync output to the Brown & Yellow leads, which did nothing if memory recalls... (as in I'm not too sure)

Does anyone know what the other 2 leads are?

November 3rd, 2006, 09:44 PM
You should use a multi-meter to check which wires go to a connector. Some meters have a setting especially for this, others have a resistance setting which will also work.

November 3rd, 2006, 09:49 PM

...So basically that's what I'm getting...

November 4th, 2006, 01:00 AM
See http://www.vintage-computer.com/vcforum/archive/index.php/t-4346.html for a similar story.
In that story, because we knew that the video card and monitor used the same video standard (EGA), the resolution was only a case of working out the pin assignments.

In your story, if you don't know for a fact that the video source and monitor use the same video standard/s, then the connection may never work due to any of the following:
* composite sync versus separated sync
* polarity of sync signals
* frequency of sync signals
* voltage level of video/sync signals

November 4th, 2006, 01:22 AM
The monitor is RGB, & made in 1987, so I doubt it would leave the 15KHz range.

November 6th, 2006, 05:26 PM
Finding monitors that scan down to 15khz can be a pain. All normal CGA and EGA montors AFAIK, are fixed in the 30khz range.

If you need 15khz, check the Apple IIgs faq. They have a list of monitors that can go down to that range. It includes the Nec Multisync IIA, I believe, the CM-8 color computer 3 monitor, the IIgs monitor, and a few Commodore models.

One trick that I plan to try sometime is to get an old medical/broadcast video monitor off of ebay. Those things have every weird color/sync connector imaginable on the back, and would probably be capable of working with just about any low-sync RGB or composite video.