        Using the Atari ST with a standard PC (VGA/SVGA) monitor
        --------------------------------------------------------

This text file along with the accompanying illustrations shows you how to
make a cable allowing a standard PC monitor to be used with with your Atari
ST in "ST high" mode (640x400 pixels, black/white).

The two illustrations are supplied in various formats so that they can be
viewed (and printed) on any computer, be it an Atari ST, PC, Mac etc.:

vga_16.gif			16 colour GIF (connection diagram)
vga_2.img			Black/white IMG (connection diagram)

resistor.gif		16 colour GIF (trimmer illustration)
res_2.img			Black/white IMG (trimmer illustration)



Overview and features
---------------------
First of all, make sure your PC monitor is able to handle 
the Atari ST's frequencies which are as follows:

  35.7 KHz	horizontal
  71.2 Hz   vertical
  
Most modern PC monitors are able to handle this, but please check 
with the monitor's user manual before connecting it to the Atari ST.

A couple of common misunderstandings which need to be cleared up:

a) You don't get a bigger desktop (e.g. more room for windows, icons etc.).
   The WHOLE picture just gets bigger. Imagine looking at the small 
   Atari monitor with a magnifying glass.
   
b) You don't get a colour picture even though the PC monitor is able to 
   display colour. The Atari ST isn't capable of displaying high-resolution 
   colour. You can however choose to have the COMPLETE picture shown in a 
   particular colour if you wish (using variable resistors/trimmers to 
   fine tune the output).
   
- Any number of PC monitors can be used (as long as the frequency 
  specifications are met): large screen, flat LCD displays, projectors etc.
- Audio can be connected to a PC multimedia speaker set, amplifier or 
  the monitor itself, provided it has a speaker
- If the user wants to, the cable can be made to allow for colour adjustments 
  meaning that the picture can either be black/white like the Atari ST monitor, 
  blue, green, yellow, orange, red or anything in between!
   


Parts list
----------
Description                             Amount
-----------------------------------------------------------------------
- 4 pin (or more) screened cable        2 metres (or any desired length)
  7mm diameter
- 13 pin DIN (male) connector           1
- 15 pin HD D-sub (female) connector    1
  (HD=high density)
- 47 Ohm resistors (small)              3 (for black/white display)
   or...
  100 Ohm trimmer resistors (miniature) 3 (for colour adjustable display)      
  (as small as you can get. They will 
  have to fit inside the 15 pin connector!)


... and if you want to add audio output (using the monitor's speaker or 
    external multimedia speakers:
    
- 1 (or 2) pin screened cable           2 metres (or any desired length)
  4mm diameter
- 3.5mm stereo jack socket              1 (if using multimedia speakers)
   or...
  3.5mm stereo jack plug                1 (if using monitor's speaker)
     

   
Building instructions
---------------------
Refer to the connection diagrams while reading the instructions here to 
get the full story:

1) Cut the video (and audio if needed) cables to the length(s) you need 
   and prepare them so they can be soldered to the connectors.

2) Slide the cables through the connector hoods. 
   It's not much fun realizing that you've forgotten them after having spent 
   a lot of time making perfect solder connections to the wire ends!
   
3) Connect the common ground pins of the 15-pin HD D-sub connector together 
   as shown in the wiring diagram (pins 4,5,6,7,8,10 and 11). I've personally 
   found it most practical to cut off unused ends of resistors or capacitors 
   for this.
   
4) Connect pins 4 and 13 (13-pin DIN connector) together. 
   This is best done with a small wire.
   
5) a) Solder the three resistors to pins 1,2 and 3 of the 15-pin HD D-sub 
      connector if you want a fixed black/white display (works fine for 
      most people).
      Continue by connecting the common ends together.
   or.....
   
   b) Solder one end each trimmer resistor to pins 1,2 and 3 of 
      the 15-pin HD D-sub connector if you want to be able to adjust the 
      output colour/level of the display (for those of you who like to 
      have options).
      Continue by connecting the common ends together.
      Solder the unused ends to the wiper pin of each trimmer.
 
6) Connect the wires of the 13-pin DIN and 15 pin HD D-sub connectors 
   together as shown in the connection diagram. It might be a good 
   idea to solder the middle pins of the connectors first as they'll 
   be harder to reach once other wires have been soldered to the outer 
   pins:
   
     13-pin DIN         15 pin HD D-sub
     -----------------------------------------------       
     Pin 9 (Hsync)      Pin 13 (Hsync)        
     Pin 12 (Vsync)     Pin 14 (Vsync)
     Pin 4/13 (Ground)  Pin 4/5/6/7/8/10/11 (Ground)
 
7) Connect the wire end from pin 11 (13-pin DIN connector) to the common 
   ends of the resistor (or trimmer) array.
   
8) If you want audio output, connect of the wire-end pairs to the 13-pin 
   DIN connector, and the other to the 3.5mm jack. 
   The Atari ST audio output is in mono, but since the other end 
   (speakers in monitor or stand-alone multimedia speakers) will most likely 
   handle stereo audio you will need to connect the signal wire to both 
   left and right sides in the jack connector.
   Depending on what kind of connector is at the other end you will need 
   either a jack connector or a jack socket.  
       
9) Check all your connections. If you have someone impartial around, 
   let him/her check as well.
   
10) Don't slide the connector hoods over the connectors just yet, but 
    try it all out first.
    You should get the same display as you've always been getting. 
    You might have to adjust the monitor as the display might have shifted 
    to one or the other side of the monitor. Nothing to worry about.
    If you've chosen to go for the trimmer version of the cable, try adjusting 
    each trimmer so that you get the colour you want.
    
11) If everything seems to be working the way it should you can disconnect 
    the cable (keep in mind that the Atari ST reboots every time that end of 
    the cable is removed) and finalize the project by sliding the hoods in 
    place, over the connectors and assembling the 15 pin HD D-sub connector's 
    housing. 
    Make sure that no wires short circuit. Use insulating tape between wires 
    and connection pins if necessary.
    
            
 
Good luck!



Hallvard Tangeraas, Oslo, Norway
 30-September-2003
