From
um-math!mailrus!ames!pasteur!ucbvax!decwrl!ldp.dec.com!weaver Sun Sep 18
04:57:30 EDT 1988
NEC MultiSync II to Atari
ST
--- --------- -- -- ----- --
Copyright (c) 1988 David S.
Weaver
All rights reserved
This file may be copied freely only with
the inclusion of the above
copyright notice for non-commercial
use.
The NEC MultiSync II is an easy monitor to
connect to your ST if
you want a monitor that can be used with systems other
than just the
Atari ST. The following text describes how to build a
switch box
to connect the MultiSync II to the ST to allow use of color or
monochrome
with the flick of a switch.
Some specs for the MultiSync II and
Atari:
NEC MultiSync
II
Atari
low medium
high
------- ------- -------
Horizontal Frequency: 15.5kHz -
35kHz 15.8kHz 31.5kHz
35.7kHz
Vertical Frequency: 50Hz -
80Hz
60Hz 60Hz 71.2kHz
Horizontal
Resolution: 800
dots
320 640 640
Vertical
Resolution: 560
lines
200 200 400
Signal
level: TTL
pos
--- ---
---
(analog)
0.7Vpp 75 ohm
pos 1.0Vpp 75
ohm
Sync Signal level: TTL
pos/neg
TTL 3.3K
neg
(analog)
0.3Vpp
neg
--- --- ---
As one can see from the chart, all the
Atari specs fall with the NEC's
except for the 35.7kHz (instead of 35kHz)
which doesn't seem to be a
problem. Also the video signals are a bit
high (1.0Vpp rather than
0.7Vpp), but it seems to be working just fine
without the addition of
any resisters. (If you want to add a resister,
you would need 107-75
ohms or 32 ohms in series for the RGB signals, if I did
my math correctly)
I initially had a problem with the NEC not
syncing to high rez mode on
the ST after powering off the monitor and then
powering it back on
again. The workaround was to either unplug the
video cable, or reboot
the ST. I decided to add a switch to break the
horizontal and
vertical sync lines. During the process, I switched the
cables I was
using to feed the DB9 connector to some that were more flexible
because I
had a problem with the signal lines breaking at the
connector. I also
grounded the DB9 connector to the shield ground in
the cable from the
Mega ST. As a result of this rework, I found I no
longer needed the
extra switch to interrupt the sync signals.
The following pin assignments are
what work when connecting an NEC
MultiSync II to a Mega ST2 for color
operation, they should work for
any of the ST series:
MultiSync
II
Mega ST
(female
DB-9)
(male 13 pin DIN)
pin 1
red
pin 7 red
pin
2
green
pin 6 green
pin
3
blue
pin 10 blue
pin
5 mode control or v sync pin 12
verticle sync
pin 4
h/v sync or h sync
pin 2 composite sync
pin 6 red
ground
pin 13 ground
pin
7 green
ground
pin 13 ground
pin
8 blue
ground
pin 13 ground
pin
9
ground
pin 13 ground
The Mega ST can also
use this combination for sync:
pin 4 h/v sync or h
sync pin 9
horizontal sync
pin 5
mode control or v sync
* not connected
For monochrome to work,
use the following connections instead of
those listed for
the same pins above:
pin
1
red
pin 11 monochrome
pin
2
green
pin 11 monochrome
pin
3
blue
pin 11 monochrome
* Connect to pin 13 (ground) if you want to increase
the
vertical size on
the screen. Not really needed as
the
front panel "v
size" switch has enough control, and
the
image size is big
enough with the "v size" switch in
the
dentented
position.
In addition, you will want to provide a
separate RCA jack to provide
an audio out connection, given that the
Multisync has no audio
capabilities:
RCA
jack
ST
connection
--------
-------------
audio
pin 1 audio
out
ground
pin 13 ground
I ended up buying a "multisync" cable
from Practical Solutions.
The Practical Solutions cable has the
following color coding:
Pin
Color
Function
----
--------------
-----------------------
1 yellow
coax audio
out
2 black
coax composite out
(composite sync on
Mega)
3
n/c
4
red
monochome monitor (ground for
monochrome)
5
n/c
6 green
coax rgb -
green
7 red
coax rgb -
red
8 blue coax shield +12V (may vary from
ST to ST)
9
black
horizontal sync
10 blue
coax
rgb-blue
11 white
coax
monochrome
12
white
vertical sync
The following was
verified with an ohm meter:
13 yellow coax shield
ground
black coax shield
ground
green coax shield
ground
red coax shield
ground
white coax shield ground
In addition the shield
appeared to be grounded as well.
I cut about a 6" length of cable off the
cable from Practical Solutions
and used it to wire in a few switches to
switch both the monochrome/color
signals and the h/v/composite signals.
This cable is much more flexible
than the cable I tried using in my first
attempt. By separating the
individual shielded cables from the bulk
wrap, you can get some very
flexible/thin shielded coax.
The switch box ended up something
like the following:
Atari ST pin 4
pole NEC Multisync-II
pin
(13 pin DIN
male) double throw (DB-9
female)
----------------- toggle switch
--------------------
+---------+
| |
Blue
Cx 10 - rgb/blue -------
|
| /--------------- rgb/blue - 3
White Cx
11 - monochrome -----/
|
| |
Green
Cx 6 - rgb/green ------
|
| /---------------rgb/green - 2
White Cx
11 - monochrome -----/
|
| |
Red
Cx 7 - rgb/red --------
|
| /---------------- rgb/red - 1
White Cx
11 - monochrome -----/
|
|
|
- n/c ------------
|
| /---------------- ground - 9
Red 4 - mono
monitor----/
|
|
|
+---------+
2 pole
*
double
throw
toggle
switch
+---------+
| |
Black
Cx 2 - comp sync ------
|
| /-------- comp/horiz sync - 4
Black 9 - horiz sync
-----/
|
|
|
| |
White
Sh 13 - ground ---------
|
| /--------- mode/vert sync - 5
White 12 - vert sync ------/
|
|
|
+---------+
* This switch is purely optional, it allows
use of both types
of video sync, and will
ground the mode pin to increase the
vertical
size when composite sync is switched in.
Red Sh 13 -
ground ------------------------ red ground - 6
Green
Sh 13 - ground ---------------------- green ground -
7
13
- ground ----------------------- blue ground -
8
13
- ground ---------------------------- ground - 9
Yellow C 1 -
audio out --------------------- RCA signal line
Yellow S
13 - ground ------------------------ RCA ground line
shield -------------------------------------- shield
Note: Do NOT
connect pin 8 (Blue coaxial shield) to any
other
pins/signals. This pin may have +12 volts on it.
Make
sure that
you insulate the shield very well on this
line
so it won't
make accidental contact with another signal.
When the cable is all
built, use an ohm meter and make sure that you
have no shorts. When you
actually want to hook it up to test it, set
the switches on the back of the
MultiSync II to the following:
Switch
State
manual switch
on
mode
switch gray
(shouldn't matter, digital only)
color mode switch 64 (shouldn't
matter, digital only)
Set the switches on the front to the
following:
Switch
State
v
posi
adjust after powering on
v
size
adjust after powering on
h
posi
adjust after powering on
h
size
on
text
off (shouldn't matter, digital
only)
text
color white
(shouldn't matter, digital only)
Now turn on power and you are on your
way. Note that for all of the
cabling of video signals, I used shielded
cables (highly recommended)
and soldered all the coax shields together and to
the ground pins
(use a smaller braided cable to actually connect between the
shields
and ground pins).
#
Part#
Description
Price: Source:
-
-----
-----------
------ -------
1 76108
16-130 1 7/16"x4 13/32"x3 7/32" black box
8.99 A/E
1 69377
904 female RCA
connector
0.59 A/E
1
276-1538 female DB9 connector, solder
type 2.49 R/S
1
53055 205817-1 female screwlocks (for
DB9)
1.49 A/E
1 22104 7401SYZQ 4 pole, double
throw, toggle switch 10.99 A/E
1
22048 7301SYZQ 3 pole, double throw, toggle switch
8.09 A/E
1 76292 11-304 5/8"
OD, 1/2" ID rubber grommet
0.99 A/E
1
Atari ST "multisync"
cable
24.98
P/S
-------
Total: $ 58.61
Optional hardware for audio:
1
277-1008B 200mW
Amplifier-Speaker
11.95 R/S
1
273-1552 9-Volt Battery
Eliminator
4.95 R/S
1
42-2444 6' Phono to Mini Phono
Plug Cable 1.99
R/S
-------
Total: $
18.89
Grand Total: $ 77.50
P/S
A/E
R/S
Practical
Solutions Active
Electronics Radio Shack
1930
E. Grant Road 133 Flanders
Road
Tuscon, Arizona, 85719 Westborough,
MA 01581
(602)884-9612
1-800-343-0874
(617) 366-8899
You will also need various drill bits,
solder, and some tool to cut a
hole for the DB9 connector into the plastic
end of the aluminum/plastic
box. The grommet is to protect the ST
monitor cable entering the box.
Disclaimers:
o This
hookup worked for my Mega ST, I make no gaurantees it will
work
correctly on your ST, it has also been tested on a
1040 ST using the
h & v sync and seemed to work just
fine.
o I have no connection with NEC, Practical
Solutions, Active Electronics
or Radio Shack.