Sync on Green RGB video

jim stephens jwsmail at
Sat Nov 18 18:01:35 CST 2017

On 11/18/2017 3:44 PM, william degnan via cctech wrote:
> On Nov 18, 2017 4:09 PM, "Douglas Taylor via cctech" <cctech at>
> wrote:
>> I have a couple of vaxes that output 'unique' video, Alpha 3000 300,
> Alpha 3000 400, Vax 4000 VLC, and Vax Station 3100 M76.
>> The Alpha and VLC each have a 3W3 type of connector and the 3100 has a 15
> pin DEC designed connector.
>> What does it take to connect these to inexpensive, modern VGA light
> weight monitors?
>> Doug
> I have played around with that problem.  If you have a converter to get
> into a VGA port a newer high-end vga display will be able to adjust, but
> not a cheap one.  Because I use my vice vga/digital display for mode stuff,
> I use a huge SGI color display for all of my 3w3 outputting systems and I
> just switch the cable around.  If you could imagine 5 or 6 systems
> clustered around the one display.
> I am sure someone here has a technical explanation, but in a nutshell the
> 3W3 world signal isn't the same as a standard vga and cheap vga displays
> can't handle the refresh rate.  Someone will prob. refine my answer but
> that's why you can't just stick an adapter on there.
> Bill Degnan
> twitter: billdeg
The 13w3 Sun and the like world of video is different than the three 
wire sync on green video from Dec.  There is a feature on a lot of the 
Sony displays, including the ones that Dec rebadged that supported the 
sync on green.

There is a Raritan converter for Sun keyboard and video conversion to 
PS2 and VGA that is powered off the 13W3 connector to solve the problem 
for the Sun systems.

Also note there is a monochrome option with just a single coax populated 
in the 13W3 for sun.  I'm currently getting ready to hook it up to the 
above noted converter, can report back whether it works.  FWIW the 
system is an IPC Sparc 1 mini system.

I have the DEC Sony monitor, and  a friend and I are collecting 
information to make a general DEC Vax sync on green / Pro 3xx / Rainbow 
/ Decmate board / jumper board / connector adapter for all the crap we 
have.  Output will be VGA.

Right now we've run the video to regular RS-170 monitor.  Levels weren't 
necessarily happy with direct connection but video showed up.


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