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.