Help, get DEC VR290 monitor working with PC linux

Help, get DEC VR290 monitor working with PC linux

Post by i.. » Sun, 06 Apr 1997 04:00:00



Hi,

I recently got hold of an old DEC VR290-AD 19" color monitor
which I would like to use as a display for Xwindows. The
monitor is of a fixed frequency type, resolution 1024x864,
horizontal scan 54kHz and vertical refresh rate 60Hz.
Furthermore, the fixed frequency monitor uses RGB signals
with a composite sync on green, which is incompatible with
a standard PC VGA adapter.

To connect the monitor to a PC I have:
(1) combined the two sync signals (with a handful of ICs)
    and superimposed the sync signal on the Green video signal.
    The circuit enables the DEC monitor to sync on the video.

(2) set up the Xserver to provide the correct horizontal
    and vertical sync (at least I think :-/ )
    with:
    Modeline "1024x846" 66 1024 1088 1168 1248 864 868 872 880

All this will give me a stable picture, but it looks like
the sync pulse occurs at the wrong time.

The problem:
The picture I am getting shows the Xdesktop starting somewhere
in the middle of the screen, leaving the right side, and then
re-appearing on the left.

Has anyone succesfully connected this monitor to a PC? If
so, how? It would be a shame to let this (once) expensive monitor
go to waste.

Kind regards, Ivo

 
 
 

Help, get DEC VR290 monitor working with PC linux

Post by i.. » Sun, 06 Apr 1997 04:00:00


Hi,

I recently got hold of an old DEC VR290-AD 19" color monitor
which I would like to use as a display for Xwindows. The
monitor is of a fixed frequency type, resolution 1024x864,
horizontal scan 54kHz and vertical refresh rate 60Hz.
Furthermore, the fixed frequency monitor uses RGB signals
with a composite sync on green, which is incompatible with
a standard PC VGA adapter.

To connect the monitor to a PC I have:
(1) combined the two sync signals (with a handful of ICs)
    and superimposed the sync signal on the Green video signal.
    The circuit enables the DEC monitor to sync on the video.

(2) set up the Xserver to provide the correct horizontal
    and vertical sync (at least I think :-/ )
    with:
    Modeline "1024x846" 66 1024 1088 1168 1248 864 868 872 880

All this will give me a stable picture, but it looks like
the sync pulse occurs at the wrong time.

The problem:
The picture I am getting shows the Xdesktop starting somewhere
in the middle of the screen, leaving the right side, and then
re-appearing on the left.

Has anyone succesfully connected this monitor to a PC? If
so, how? It would be a shame to let this (once) expensive monitor
go to waste.

Kind regards, Ivo

 
 
 

Help, get DEC VR290 monitor working with PC linux

Post by i.. » Sun, 06 Apr 1997 04:00:00


Hi,

I recently got hold of an old DEC VR290-AD 19" color monitor
which I would like to use as a display for Xwindows. The
monitor is of a fixed frequency type, resolution 1024x864,
horizontal scan 54kHz and vertical refresh rate 60Hz.
Furthermore, the fixed frequency monitor uses RGB signals
with a composite sync on green, which is incompatible with
a standard PC VGA adapter.

To connect the monitor to a PC I have:
(1) combined the two sync signals (with a handful of ICs)
    and superimposed the sync signal on the Green video signal.
    The circuit enables the DEC monitor to sync on the video.

(2) set up the Xserver to provide the correct horizontal
    and vertical sync (at least I think :-/ )
    with:
    Modeline "1024x846" 66 1024 1088 1168 1248 864 868 872 880

All this will give me a stable picture, but it looks like
the sync pulse occurs at the wrong time.

The problem:
The picture I am getting shows the Xdesktop starting somewhere
in the middle of the screen, leaving the right side, and then
re-appearing on the left.

Has anyone succesfully connected this monitor to a PC? If
so, how? It would be a shame to let this (once) expensive monitor
go to waste.

Kind regards, Ivo

 
 
 

Help, get DEC VR290 monitor working with PC linux

Post by Dick Erlach » Tue, 08 Apr 1997 04:00:00



>Hi,

>I recently got hold of an old DEC VR290-AD 19" color monitor
>which I would like to use as a display for Xwindows. The
>monitor is of a fixed frequency type, resolution 1024x864,
>horizontal scan 54kHz and vertical refresh rate 60Hz.
>Furthermore, the fixed frequency monitor uses RGB signals
>with a composite sync on green, which is incompatible with
>a standard PC VGA adapter.

>To connect the monitor to a PC I have:
>(1) combined the two sync signals (with a handful of ICs)
>    and superimposed the sync signal on the Green video signal.
>    The circuit enables the DEC monitor to sync on the video.

>(2) set up the Xserver to provide the correct horizontal
>    and vertical sync (at least I think :-/ )
>    with:
>    Modeline "1024x846" 66 1024 1088 1168 1248 864 868 872 880

>All this will give me a stable picture, but it looks like
>the sync pulse occurs at the wrong time.

>The problem:
>The picture I am getting shows the Xdesktop starting somewhere
>in the middle of the screen, leaving the right side, and then
>re-appearing on the left.

>Has anyone succesfully connected this monitor to a PC? If
>so, how? It would be a shame to let this (once) expensive monitor
>go to waste.

>Kind regards, Ivo

===================================================================
These are goofy monitors which require odd sync and blanking relationships.  A
handful of IC's is absolutely unnecessary in order to make it work.  What's
required is a program which directly programs the video controller, and a
500-ohm resistor from composite blanking on the application connector to the
green video line at the series resistor between the connector to the monitor
and the video DAC, which drives the green video.  This will bias the green
positive, but the blanking is close enough to the required sync that you can
use it to get close.  If you're interested, there's a better circuit I can
send you which uses a transistor array and a few resistors and requires you
provide a negative supply, e.g. the -5Vdc from the ISA bus.

If you're determined, you can do this.

Let me know if you need details.

regards,

Dick

 
 
 

Help, get DEC VR290 monitor working with PC linux

Post by Rune Fog Hans » Tue, 08 Apr 1997 04:00:00



>Hi,
>I recently got hold of an old DEC VR290-AD 19" color monitor
>which I would like to use as a display for Xwindows. The
>monitor is of a fixed frequency type, resolution 1024x864,
>horizontal scan 54kHz and vertical refresh rate 60Hz.
>Furthermore, the fixed frequency monitor uses RGB signals
>with a composite sync on green, which is incompatible with
>a standard PC VGA adapter.
>To connect the monitor to a PC I have:
>(1) combined the two sync signals (with a handful of ICs)
>    and superimposed the sync signal on the Green video signal.
>    The circuit enables the DEC monitor to sync on the video.
>(2) set up the Xserver to provide the correct horizontal
>    and vertical sync (at least I think :-/ )
>    with:
>    Modeline "1024x846" 66 1024 1088 1168 1248 864 868 872 880
>All this will give me a stable picture, but it looks like
>the sync pulse occurs at the wrong time.
>The problem:
>The picture I am getting shows the Xdesktop starting somewhere
>in the middle of the screen, leaving the right side, and then
>re-appearing on the left.

Try fiddeling with the polarity of the sync-signals.
My VR320-DA accepts one polarity, but screws up the display
with the reverse polarity. Cant remember which though.

Good luck
Rune