I have the same problem with a cheap 19" LCD VGA Screen. What i made is
to seperate the required sync signal with an LM1881 Video Sync
Seperator. I used the standard application from the TI datasheet.The
only difference is that i used an viariable resistor on pin 6 to adjust
to the Sync Frequency. That is running with my Vax Station 4000 / 60.
Marco Rauhut
Am 19.11.2017 um 04:57 schrieb Douglas Taylor via cctech:
On 11/18/2017 6:44 PM, william degnan wrote:
On Nov 18, 2017 4:09 PM, "Douglas Taylor via cctech"
<cctech@classiccmp.org <mailto:cctech@classiccmp.org>> 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
vintagecomputer.net <http://vintagecomputer.net>
I ran into a similar comment somewhere on the internet somewhere (it's
a big place) that you had to make sure that the LCD monitor supported
the H,V rates put out by the DEC video frame buffer.
