Table of Contents
Japanese RGB-15 Connector
This connector is the standard for many pre-DOS/V (IBM compatible) computers in Japan. The PC-9801, X68000 and FM Towns all used this pinout, or similar variants of it.
Pay attention to the differences, they are important! Specifically, watch the Ys line. This is a 5V signal from the machine that tells the monitor a computer is actively sending video. Without this signal many monitors will not attempt to show anything, and my NEC monitor simply goes into standby. Since many devices don't include 5V (for example, VGA) you may have to add this yourself. I wired mine to a USB connector, and plug that in to any USB device to activate the monitor.
NOTE the numbers are usually visible on the connector itself. If you're looking at the business end of the female connector, pin 1 is on the right. On a male connector it's on the left.
X68000
| Pin | Function | Pin | Function |
|---|---|---|---|
| 1 | Red | 9 | NC |
| 2 | Ground | 10 | Audio L |
| 3 | Green | 11 | Audio R |
| 4 | Ground | 12 | Ground |
| 5 | Blue | 13 | NC |
| 6 | Ground | 14 | H-Sync |
| 7 | Ys | 15 | V-Sync |
| 8 | Ground | ||
- Ys = computer data present. Usually +5V
PC 9801
The PC-9801 connector is nearly the same as the X68000. The differences are very minor: pins 9 and 13 are used for the 9801, but are not connected on the X68000.
| Pin | Function | Pin | Function |
|---|---|---|---|
| 1 | Red | 9 | Ys |
| 2 | Ground | 10 | AV Control |
| 3 | Green | 11 | Mode |
| 4 | Ground | 12 | Ground |
| 5 | Blue | 13 | Dot Clock |
| 6 | Ground | 14 | H-Sync |
| 7 | Ys | 15 | V-Sync |
| 8 | Ground | ||
- Ys = computer data present. Usually +5V
FM Towns
| Pin | Function | Pin | Function |
|---|---|---|---|
| 1 | Red | 9 | Ys |
| 2 | Ground | 10 | AV Control |
| 3 | Green | 11 | Mode |
| 4 | Ground | 12 | Ground |
| 5 | Blue | 13 | Dot Clock |
| 6 | Ground | 14 | H-Sync |
| 7 | C-Sync | 15 | V-Sync |
| 8 | Ground | ||
- Note that some FMTowns systems used a VGA connector.
- Ys = computer data present. Usually +5V
CAVEATS
- Not all systems put out power on pin 7. Normally +5v, some devices (like the X-RGB2) leave this pin disconnected. You can add power to your cables, for monitors that require it, following these directions.
- Remember that the pin numbers are almost always found on the connector itself.
- CRITICAL: H and V sync are TTL level (5Vpp) If you make a SCART cable and tie pins together, you must use a resistor (470ohm - NOT CONFIRMED) to lower voltages to safe levels for 75ohm / 0.3Vpp CSYNC or else you’ll damage the X68K or your display device (eg XRGB mini)
Credit:
- Some of this info came from this Japanese page.