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1989-04-05
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313 lines
NEC MULTISYNCH MONITOR SPECS
__________________________________________________________________________
PROBING YOUR ST by W.K. Whitton
(From a 'SEWER DOC' disc. If it isn't PD - apologies to W.K. Whitton)
__________________________________________________________________________
I am sure you have heard the old axiom referring to the fact that two of
an item is usually better than one, as in "two heads are better than one"
and the like. This is not necessarily so as we shall find out rather
nicely in this article!
Most ST owners will agree that our SC1224 RGB monitor has excellent
graphics capability, especially when one is using it in conjunction with
one of the fabulous paint packages available for the ST, or when one is
partaking of the numerous quality games you can enjoy also. But, when the
owner tries to do any amount of serious word processing, his eyes may be
the victim of strain and uneasiness. The best cure for this (until now),
was the SM124 monochrome monitor. This display is extremely easy on the
eyes, they will thank you for it! (In fact we have been in touch with a
number of Mac owners, and assisted them in rewiring it to use with their
computer, the display was larger than the one they originally received,
and MUCH less expensive!) This brings to the forefront another problem
...you now, if you indeed to be serious about your ST and business type
applications, need to juggle 2 monitors, and in anybody's book, is not an
easy task!
If you want to use only ONE monitor, now there is an alternative! Read
on:
"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. If you have any questions, feel free to contact the
author on CompuServe (76456,2604) or Delphi (DSWEAVER).
The NEC MultiSync II is a great monitor to buy if you want a monitor that
you can migrate to another system when the time comes that you need higher
resolution color.
The specs are as follows:
NEC MultiSync II Atari
low medium high
------- ------- -------
Horizontal Bandwidth: 15.5kHz - 35kHz 15.8kHz 31.5kHz 35.7kHz
Vertical Bandwidth: 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
resistors. (If you want to add a resistor, you would need 107-75 ohms or
32 ohms in series for the RGB signals, if I did my math correctly)
EDITORS NOTE: A value of 68 ohms, 1/4 or 1/2 watt will work fine in this
application, and furthermore, are rather easy to procure! 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 work
around 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 vertical 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
EDITORS NOTE: In order for this to work with the 520 and 1040ST, you must
also connect these pins:
MultiSync II 520/1040 ST
pin 5 H sync pin 9 horizontal sync
pin 6 V sync (mode control) pin 6 vertical sync
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 detent 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 monochrome mon (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/small 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.
EDITORS NOTE: Please clip this lead as short as possible to avoid
accidental contact with adjoining leads. 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 pos adjust after powering on
v size adjust after powering on
h pos 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
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.
Disclaimer:
o This hookup worked for my Mega ST, I make no guarantees it will work
correctly on your ST.
o I have no connection with NEC, Pratical Solutions, Activer Electronics
or Radio Shack."
After this mod is made, you will find that you will need to readjust the
Vertical position, Vertical size and Horizontal size controls located on
the front panel of the monitor.
Set the "Manual" switch to the manual position. Set the "Text" switch to
off, and the "Text Color" switch to white.
If this project seems to be a bit much for you, you can buy an already
assembled similar Multisync adapter. It adds the feature of having a
composite input, so you can use your Atari 8 bit with a Multisync (strange
sounding isn't it?), or the video out of your VCR, and that way watch your
favorite movie while your computer is busy doing other things (now THATS
multitasking at its best!).
The monochrome display from your ST, with this box, will be one of two
possibilities that you choose:
Black Text on Green screen
White Text on Green screen