MULTISYNC SWITCH CABLE on Atari ST/E by Marcello Vezzelli

╔════════════════════════════════════════════════════════════════════════╗
║                     MULTISYNC SWITCH CABLE on Atari ST/E               ║
║                                                                        ║
║  How build a humble "cable" to connect your ST to a multisync monitor  ║
║           and switching from MONO to COLOR in a flash!                 ║
║                                                                        ║
║  By Marcello Vezzelli - Thanks to Ivo Elmi for testing...              ║
Ã────────────────────────────────────────────────────────────────────────Â
║  This came from                                                        ║
║   THE ST HARDWARE HACK PAGE                                            ║
║   http://www.geocities.com/SiliconValley/Way/8016                      ║
╚════════════════════════════════════════════════════════════════════════╝

Hi to all,
it's so boring having to switch between the two monitors... plug, unplug,
replug, reunplug... so, for those who can afford a multisync monitor,
this is a simple project which eliminates this boredom.

If you have a multisync monitor, e.g. Nec MultiSync 3D, you can build this
simple cable, that allows you to switch between mono and color without
disconnecting and reconnecting (hey, your monitor is a multisync, so it can
display both mono and colour...)

*************************** WARNING !!!!!!!!!!!!!!! ***********************

THIS SWITCH WAS DONE FOR A NEC MULTISYNC 3D. IT MAY NOT WORK WITH ANOTHER
KIND OF MONITOR. BE SURE YOUR MONITOR HAS THE SAME CONNECTIONS OF THOSE
SHOWN BELOW. (They just are standard VGA connections.)

It's not my fault if your switch doesn't work of if you destroy your monitor.
I'm not responsible of the content of this DOC.
If nobody alter this text, I assure you that connection works with the NEC 3D
(if you do all well!!). You do this interface at your own risk.
I'm using now this cable with my NEC 3D with no problems at all.

***************************************************************************

Once you're warned, here's the project:

You need:

- A Multisync monitor. NEC 3d or Commodore 1960 just works great.
  The monitor you choose MUST accept horizontal frequencies between 15Khz
  and 35Khz. The critical one is 15Khz (it's the color mode). If your monitor
  can't handle correctly 15Khz, YOU'RE STUCK IN MONO MODE.
  If you're not sure about monitor capabilities, try before buy!
  Some monitors are dual-frequency... avoid them!
  Some others have a trimmer for H-freq... if you don't mind tweaking every
  time you change rez, buy one of these... (try before! No one assures that
  can handle 15Khz!)
  Forget CGA, EGA, Hercules and Macintosh monitors. :-/

- 1 quadruple switch (two positions, four separated lines, for a total of 12
  contacts)

- a 100 ohm trimmer

- a metallic box, or instead, a shielded plastic box

- a 15-pin female connector (standard vga)

- an Atari monitor connector (13 pin, see your manual for details)

- about 2 metres of 8-wires shielded cable

****  Are you ready? Let's start!

1) Cut the cable in two parts. The shorter the cable, the best. One part goes
   from the ST to the switch box. Other part goes from switch box to VGA
   connector of the monitor.

2) Solder the cable shield to the metallic part of the ST monitor connector.

3) Solder a wire in each of this pin of the Atari monitor connector:

 4,6,7,9,10,11,12,13 (see your manual, or this scheme, or whatever :)

 Monitor socket seen from the back of your Atari:

        4  3  2  1
        8  7  6  5
        12 11 10 9
            13

 You can't miss it! Better if you note down the corrispondence between
 colours and pin numbers.

4) Now take the switch. It look like that (it's the back!):
   Let's name the pins.

        |-----------|
        |A1 A2 A3 A4|
        |           | > Mono
        |I1 I2 I3 I4|
        |           | > Color
        |B1 B2 B3 B4|
        |-----------|

5) Drill two holes in the box, one in front of the other.
   Or if you like, both holes in a side.

6) Insert here the two pieces of cable.
   In one of this you've just soldered the Atari socket.
   It should look like this:

                       ----------------         Atari Socket
                       |              |             /-------|
  To multisync ********|**    X     **|*********OOOOE       |   to Atari
                       |              |             \-------|
                       ----------------
                              ^
                           This is
                         the switch (X)

  Or like this:

                                                  Atari Socket
                       ----------------             /-------|
                       |            **|*********OOOOE       |   to Atari
                       |      X       |             \-------|
                       |            **|*********To Multisync
                       ----------------
                              ^
                           This is
                         the switch (X)


7) Now solder: (number refers to ST connector)

 7-B2  6-B3  10-B4 (These are the RGB signal);

 11-central pin of the trimmer

 left (or right, it's the same) pin of the trimmer-A2-A3-A4;


 Maybe you'll need a short naked wire to solder all the three pin altogheter.

 4-A1 (this is the monochrome detect)

 13-I1 (this is the ground).


8) Now let's work around the vga socket.

 Solder togheter pins: (the pin numbers are in the back of the socket, so
 you can't make mistakes...)

 4-6-7-8-10-11 with the pin 13 of the Atari socket (all this pins are ground)
 or to the cable shield;

9) Then solder (always speaking about VGA socket):

 1-I2  2-I3  3-I4 (these are R/G/B signals)

 Ok, the switch is almost ready... now let's connect other signals:
 The first number refer to ATARI SOCKET, the second to VGA SOCKET (be careful!)
 (you have to connect directly the wires together)

 12-14 (this is V-Sync)

 9-13 (this is H-Sync)


10) Solder the two cable shields together...

                   *********  F I N I S H E D ! ! ! **********

Fit the switch on the upper side of the box, drilling a hole.

Check connections you've made: be sure you haven't made a mistake. It's not
 so difficult...

Everything ok? Let's plug and go!!!

Turn on both monitor and computer, and, depending from the position of the
 switch, you're in mono o in colour mode. Adjust the screen using the monitor
 controls: you should see quite a good and sharp picture.

If you are in mono mode, let's adjust the trimmer: turn the trimmer left or
 right until you find a good light contrast.

If you cannot see anything in your monitor something went wrong (BLEACH).
Check connections or adjust the monitor (maybe brightness was setted to zero).

Try the other position of the switch. The computer resets and you have
changed resolution. Adjust the monitor... done!!!

-----------------------------------------------------------------------------
If you have a NEC multisync 3D, you can "save" the screen configuration,
using a switch. Very very very handy!!! (refer to monitor manual...)
-----------------------------------------------------------------------------

*****************************************************************************
If you still have some troubles, don't hexitate, mail me!
vezz@geocities.com
*****************************************************************************

That's all folk!!! See ya later....

Ciao, Marcello. (From Modena, Italy)

P.S.: not so a good English... but it should be readable. :-)