Very Computer

BAJ
-----------------------------------------

: Hi all,

: I have a wonderful  BIG greyscale Hi-Rez.-Monitor.
: It is called DEC VR 262 and used to run on a VaxStation.
: Now, I would like to connect it to my PC VGA-card.
: The line/frame-frequencies are ok for my videocard, but that monitor
: has a _composite video input_. Unfortunately, DEC does not publish
: schematics of their monitors.

: Has anybody connected one of those monitors to a PC yet?

Hold on to your hat.  In the latest Nuts & Volts mag, Jan '95, P.61,
there is a schematic for connecting a DEC VT-260 to an SVGA card.  It
says that the VT-260 is more or less RS-170 video levels.  The circuit
uses a 4066 XOR gate, a transistor, a few diodes and resistors.

BTW the Compuserve ID# for T & L Publications (N & V) is

: What is easier: Make a VGA-style (v+h+video) input at the DEC-monitor?
:                 Make a composite video-signal out of a VGA-output?

: It would be great if anybody could fax me the schematics for that monitor
: or for a VGA-to composite circuit (I remember in the old appleII this was
: done by a transistor and three resistors).
: ( BTW I am an EE and familiar with video-stuff)

---------------------------------

Quote:

>>>The problem: The STealth has the 15pin  VGA connector.
>>>             The DEC VR320 has 3 coax inputs, R G B and
>>>             no others.  It seems that the Sync is built into
>>>             the 3 inputs.  Does anyone have any idea of
>>>             how I can interface the two?

>>I don't think the sync is built into those 3 inputs, so you may have
>>trouble there.

>The sync is sent on the green signal.  Other than that I can't help.
>I've been looking for exactly this thing but not found it.  The problems
>lies in that VGA has separate sync signals and something must encode these
>into the green.  Thus my conclusion was that it can not be done simply
>by wiring but that some other hardware may be required.

--
Another random extraction from the mental bit stream of...
Byron A. Jeff - PhD student operating in parallel - And Using Linux!

-Brian

While cables to convert VGA to 3 or 4 BNC interfaces are readily available,
unless you have been lucky enough to pick up a multi-sync monitor, it
won't work with your PC.  Oh, you can probably tinker with the XFree
parameters if your video card supports it and get XWindows up, but
how are you planning to boot?  Standard DOS Text mode just won't
display properly on this monitor.  Believe me, I've tried.

There are some $500 video cards out there that support these monitors
but that's out of your range.  I suggest you give it to someone who
can use it, and that's someone who owns a workstation.  Either that
or you can give it to someone who will insist he can make it work
on his PC and watch him try.  These people are easy to identify,
they're the ones with the ba*ts and garage's full of dead and
"salvaged" computer parts.

Jim (wanna see my ba*t?) Lewczyk

--
James Lewczyk                                   1-303-223-5100 x9471

I think that's a bit harsh.  I have done exactly what the original poster
is suggesting, and it works gread.  I run an old workstation at 1280x1024
at 72 Hz from a #9GXE card (the only one which I could find which supports
sync-on-green).  I run it at run level 6 so it is always in graphics mode.
I would never attempt this with MS Windows because it crashes too often, but
it works well under Linux.  You do have to have a regular monitor fairly
close by, for problems with occur before X starts, but other than that
it works fairly well.  

My suggestion is that you first try to find out the resolution of the monitor
from the manufacturer.  If your card supports that resolution, spend a few
bucks and buy a VGA to BNC cable.  Put a BNC T connector between the
horizontal and vertical sync BNC connectors and connect it to the green.
Then connect Red and Blue, run X and plug it in.  If it works, then start
thinking of replacing your board with on which supports sync-on-green, or
build the following circuit courtesy of Jon Jenkins of DEC:

                     +5.0V
                     |
                     /
                     \ VR1 (~500)
       33uF tantalum |   ~0.3V DC
GREEN-----------||------------------------------------------------GREEN to works
tation
                                                 |
                     |                          _|
HSYNC--------|-------\                         |
             | OR    |------CSYNC--------------|    VN10KM or similar small
VSYNC--------|-------/                         |_   N channel enhancement MOSFET
             | 74HC32                            |
                                               Gnd
HSYNC, VSYNC and CSYNC all all +ve logic i.e. sync=+5.0V
and tied to ground with 4.7k carbon resisitors
To use -ve logic substitute a NAND gate

Good luck.

(Note I am a chemist and not an electrical engineer.  I recognize that lots
of people who really know what they are doing are cringing, but it worked for
me.)

--
Matt Asplund

As for boot might I suggest a dual monitor (well actually a dual video
card) setup. Since monochrome and SVGA cards can live in the same machine
it's possible to set up the boot on the mono card then run X on the
SVGA. once you get the system working you really don't need the mono monitor
just the card. You'll only need the monitor for troubleshooting.

There is one small catch when I tested this: the dumb BIOS will always
pick the SVGA card if it's present even if you choose the mono card in
the SETUP. However one could simply patch the setup.S file in Linux's boot
code to force to the mono monitor.

Quote:

>There are some $500 video cards out there that support these monitors
>but that's out of your range.

Quote:> I suggest you give it to someone who
>can use it, and that's someone who owns a workstation.  Either that
>or you can give it to someone who will insist he can make it work
>on his PC and watch him try.  These people are easy to identify,
>they're the ones with the ba*ts and garage's full of dead and
>"salvaged" computer parts.

I have access to a buttload of DEC monitors. One day I'll get around to
testing this theory out.

BAJ
--
Another random extraction from the mental bit stream of...
Byron A. Jeff - PhD student operating in parallel - And Using Linux!

Quote:>I have done exactly what the original poster is suggesting, and
>it works gread. I run an old workstation at 1280x1024 at 72 Hz
>from a #9GXE card (the only one which I could find which supports
>sync-on-green). I run it at run level 6 so it is always in graphics
>mode. I would never attempt this with MS Windows because it crashes too
>often, but it works well under Linux. You do have to have a regular
>monitor fairly close by, for problems with occur before X starts, but
>other than that it works fairly well.

Robb
________________________________________________________________________________
                    |
Robb Masters        | Systems & Software Engineer
BT N&S SSI BSEC CEC | CEC home page (BT only) - http://www.lssec.bt.co.uk:8080/
____________________|___________________________________________________________

Quote:>                     |
> Robb Masters        | Systems & Software Engineer
> BT N&S SSI BSEC CEC | CEC home page (BT only) -

There is a company that sells a video board for PCs that drive old fixed
frequency monitors.  The board uses the latest accelerator chips.
However, I have no knowledge of either performance or Linux
compatibility.  The boards are called "Photon Torpedo".  You need to get
one specific to a particular monitor.  A company that sells one for there
surplus Tek monitors is Hi-Tech Component Distributors (805)681-9961.
They may be able to order one for your DEC.  Again I have no experience
with this company, I just saw an ad in Computer Shopper.
-Greg

        Matthias
--

                        marco GmbH, 85221 Dachau        tel: +49 8131 516142

: Lucky you.
:   I think you'll have no problem using the monitor. I cannot tell you of a
: specific video card for a PC which has BNC outs, but I know I have seen
: cables which adapt the 15 (?) pins of a VGA out to RBG BNC outs. Call a local
: vendor and make sure the card is compatible before you buy; good luck.

I too have a couple of these I would like to get to work. Getting the
cable wasn't the hard part (I got mine from some mail order shop, I
forget which one) I think the problem is going to be that you need to
get a monitor that supports sync-on-green.  There are a couple of the
older #9 boards that support this. Also, I have seen a schematic for a circuit
that does this (I can dig it up if you are interested in building it).
Another problem is that you won't be able to see things during boot-up and
to run the console you will need to use svgatextmode. I just recently came
acros a company advertising video boards that are supposed to work with
single frequency sync-on-green monitors:

PCG is the Original Manufacturer of the Fixed Frequency Graphics
Controllers For over 10 years.

PHOTON TORPEDO & PHOTON TORPEDO 564- ARE TRADEMARKS OF PCG CORPORATION.
ALL OTHER TRADEMARKS ARE OF THEIR RESPECTIVE MANUFACTURER. \251 1995 PERSONAL
COMPUTER GRAPHICS, CORPORATION. ALL RIGHTS RESERVED. SPECIFICATIONS ARE
SUBJECT TO CHANGE WITHOUT NOTICE

EXT. 150 Fax# (310) 392-9033

(This was excerpted from a posting on misc.forsale.computers.workstation
I have no affiliation with this company nor personal experience with their
products).

--
=======================================================================
Eric C. Frey                    Phone: 919-966-6729; Fax: 919-966-2963;

Department of Biomedical Engineering and Department of Radiology
The University of North Carolina
152 MacNider Hall, CB 7575, Chapel Hill, NC 27599

Modeline "1024x768R" 80 1024 1072 1216 1320 768  768  769  807 -hsync -vsync
Modeline "1280x960R" 126 1280 1344 1528 1742 960  980  981 1036 -hsync -vsync

but under SVGATextMode with

"test"       80 1024 1072 1216 1320 768  768  769  807 -Hsync -Vsync font 8x8
"test1"      126 1280 1344 1528 1742 960  980  981 1036 -Hsync -Vsync font 8x8

I get a really strange effect; the screen is syncing ok but text is repeated
two or three times per line, effectively making it unusable.
Please, if anyone has any hints as to how this could be overcome, I would be
very greatful indeed!

Thanks,

Kai.

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