Hi Laurie...

 LB> Trevor, do you have any details on these SYNC adaptors, are they very
 LB> complex to make, any info you can supply would be much appreciated.
 LB> I tried to netmail you but as your system is not in the nodelist the
 LB> message bounced.
Netmail does bounce sometimes, so at the risk of incurring the wrath of
the moderator I'll post it here for you..

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Notes on VGA->RGB conversion:

I use stadard 74HC 14pin DIP gates available from any
electronics store. I use a 14pin DIP socket
originally so that I could change gate types
(OR/XOR/AND) easily. 74HC86 (XOR) works just
great with the VR320 (im using it now can
also use OR, dont understand why ??).

The VN10KM is a small signal N channel enhancement
mode mostfet also available from most electronics store.

IF the video card you are using is a standard VGA output:
(Im using a diamond stealth 64 VRAM)

1: RED video
2: Green video
3: blue video
4: monitor id bit 2
5: Ground
6: red return
7: green return
8: blue return
9: NC
10: sync return
11: monitor id bit 0
12: monitor id bit 1
13: H sync
14: V sync
15: NC

I join all the "returns" together with the ground
on the small PCB and use that as a common ground
for the RGB cable to the monitor. You can use
separate if you want to but you should join the
green return and sync returns together. I did
find some small shadowing if I didn't group
them all together.

Just a note, when you set up your video card in Windows
set it to 1280x1024x72|66 or whatever is closest
I use a VR260 (1024x864) at 1027x768{at}66Hz (check with your manual
DA or D4 are 72Hz) your VGA will not like this
frequency so either disconnect it quickly
or before you actually set the video card to this mode
(i.e. put the OK as the active control in Windows and
then connect the VR320 and hit return) My
diamond setup gives me 10 seconds to do this adjustment
When you exit you will probably have to select the
1280x1024 mode with your old VGA connected again
and from then on every time you start Windows you will
be able to view it in "big" colour mode. Note the
vr320 will not work in DOS mode as it is not a multisync
monitor so all you see when you boot up is garbage
until Windows starts, I put "win" in my autoexec.bat
file.

Note there is a danger here:
i had set up the monitor and for soeme reasonm it
did not work so I couldn't see what was going on:
my ol VGA wouldn't work and the VR wouldn't work
either so I had to find the cards .ini files and
edit by hand to get back to useable video !!

For FreeBSD/XF86 the lines are:
#VR260 monitor is 70MHz 1024x864
#VR320/319 monitor is 130MHz 1280x1024
Modeline "1280x1024" 130.81 1280 1312 1472 1696 1024 1027 1030 1063 +hsync
+vsync
Modeline "1024x864" 69.2 1024 1040 1168 1272 864 864 867 904 +hsync +vsync

The circuit to do this is as follows::

Note.
1: you may be dealing with 135MHz sqaure waves so there
   are lots of high frequency stuff around; use good
   RF practices.
2: the coupling capacitors are a safeguard to start with
   I dont use them cause they caused shadowing around
   sharp colour changes (the ol RC effect).
3: Use the XOR gate first as a test but you may need
   other gates to actually get it working
4: A CRO will be handy for final adjustment.
5: Make the device is as close as possible
   to the video outlet on the VGA card.
6: Take the 5V from the PC power supply
   inside the box. I just hooked one of the
   spare connectors which I also use for an external
   fan (pentiums being the heaters they are!). Make
   sure (check it again!!) (and again!!!) you dont get
   the 12V one!!
7: You must use a VN10KM or other
   SMALL SIGNAL
   N CHANNEL
   ENHANCEMENT MODE
   MOSFET
   others will not work !!!!!!!!



                        +5.0V
                        |
                        /
                        \ VR1 (1k carbon mini pot)
        33uF tantalum   |   ~0.3V DC in porch area
 GREEN------|----||-----|--------------------|-----GREEN to monitor|
            |----||-----|                    |
        .1-.01uF ceramic                     |
                                             |
        gnd                                  |
         |                                   |
         /                                   |
         \ 47k                               |
         /                                  _|
 HSYNC---|----|-------\                     |
              | GATE   |------CSYNC----|----||    VN10KM or similar small
 VSYNC---|----|-------/                /    |_   N channel enhancement MOSFET
         /    |                        \      |
         \                             /     gnd
         / 47k                         \ 47k
         |                             |
        gnd                           gnd

 HSYNC, VSYNC and CSYNC are grounded with 47k carbon resisitors

 GATE=LS or HC types, HC preferred.

 OR:   for -ve logic sync and no hsync during vsync
 NAND: for +ve logic sync and no hsync during vsync
 XOR:  for -ve or +ve logic sync and hysnc during vsync

 Capacitors are optional, I dont use them

 use XOR gate with DEC monitors and as a first
 shot with others, then OR gate then NAND gate.

 Get a CRO an adjust porch levels to 0.3V and
 0 level (sync level) to 0.0V
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CyA!

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