fanelli@phdvax.dec.com (01/04/87)
There have been quite a few discussions around the networks as to the methods used to attach a SONY XBR (13 inch) monitor to the RGB output of the Atari ST. None of these methods seem to work very well. With the help of an electrical engineer, we have successfully hooked up the SONY without any major effort. As it turns out, the difference between the ATARI output and the SONY input is really just a matter of matching voltage levels. The following pieces are needed: (1) Two (2) 330 ohm resitors (2) Three (3) 33 ohm resitors (3) SONY PX34 connector (34 pin analog) (4) length of 15-wire cable (5) pins to fit the connector. (6) One male, two female 15 pin connectors of any standard type (optional). The SONY wants a composite sync signal, the horizontal and vertical sync each "taking it's turn." Tying the two Atari sync lines doesn't work because the Atari signal is about twice as large as the SONY wants. The solution is to use a simple voltage divider (see diagram). The three color signals also require a slight signal reduction, provided by placing a 33-ohm resistor in each signal line. The SONY also has two pins that tell it to look for an external signal for the audio and RGB. The Atari's monochrome detect line is used to keep these two pins high. The following are the pin connects: SONY Pins Atari 30 Horizontal/Vertical sync taken off voltage divider. 27 BLUE (through 33 ohm resistor) 26 GREEN (through 33 ohm resistor) 25 RED (through 33-ohm resistor) 4,6-16 Ground (any of these pins work) 24 Tie Atari audio in/out lines together 33,34 Feed monochrome detect to both pins. Wanting to use both monochrome and color, we chopped the Atari connector off the end of a monochrome monitor. The Atari connector was attached to the purchased 15-wire cable, the other cable end being terminated with a simple 15-pin connector. The SONY PX34 and its cable, as well as the remaining cable from the monochrome monitor, were terminated with the matching 15-pin connector. This allows the monitor cable to be left attached to the ST and either monitor to be plugged in as required. This setup has been working flawlessly for quite a while. The SONY monitor is a slight bit fuzzier than the Atari SC1224 in a direct side-by-side comparison as the specs (or expectations) suggest, but does provide integration with existing audio and video electronics. Mike Fanelli Gail Wyant Pat Wyant Horizontal sync >----------------- | | \ \ 330-ohm resitor \ | |------------> to SONY pin 30 | \ \ 330-ohm resitor \ | | Vertical sync >------------------- Atari RED >-------------//////------------> SONY pin 25 33-ohm Atari GREEN >-----------//////------------> SONY pin 26 33-ohm Atari BLUE >------------//////------------> SONY pin 27 33-ohm