The ZX Spectrum 128 provides an 8-pin DIN (DIN45326) socket for video output, introduced by Sinclair and continued by Amstrad PLC after their 1986 acquisition. The connector carries TTL-level digital RGB signals (Red, Green, Blue, and a Bright-Up line) through 68-ohm series resistors derived from the ULA, making it suitable for direct connection to TTL-compatible colour monitors. A composite PAL video output is also present on the same connector, delivered at 75 ohms and 1.2 V peak-to-peak via the TEA2000 encoder. An alternative 9-pin D-type connector on the machine carries the same signals.
8 PIN DIN (DIN45326) FEMALE at the computer
8 PIN DIN (DIN45326) MALE at the monitor cable
| Pin | Name | Dir | Description |
|---|---|---|---|
| 1 | CVBS | OUT | Composite Video (PAL, 75 ohms, 1.2V p-p) |
| 2 | GND | - | Ground |
| 3 | BOUT | OUT | Bright Output |
| 4 | CSYNC | OUT | Composite Sync |
| 5 | VSYNC | OUT | Vertical Sync |
| 6 | G | OUT | Green |
| 7 | R | OUT | Red |
| 8 | B | OUT | Blue |
Notes
- Direction is Computer relative Monitor
- The 8-pin DIN socket (DIN45326) is fitted at the rear of the computer; the monitor cable uses the corresponding male plug.
- An alternative 9-pin D-type connector carries identical signals and is also present on the ZX Spectrum 128.
- RGB and Bright signals are TTL-level digital outputs driven through 68-ohm series resistors from ULA pins 19–22, suitable for TTL-compatible colour monitors.
- Composite PAL video on pin 1 is generated by the TEA2000 encoder (IC36), which also receives the same RGB signals; output impedance is 75 ohms at 1.2 V peak-to-peak.
Signals
- CVBS — Composite PAL video output, 75-ohm impedance, 1.2 V peak-to-peak, generated by the TEA2000 encoder from the digital RGB signals.
- GND — Signal ground reference.
- BOUT — Bright-Up signal; when asserted, it increases the intensity of the active RGB colour, providing the Spectrum’s 15-colour palette (8 colours × 2 brightness levels, minus duplicate black).
- CSYNC — Composite sync signal combining horizontal and vertical synchronisation for the monitor.
- VSYNC — Vertical sync output for monitors requiring a separate vertical synchronisation signal.
- G — Green video channel, TTL-level digital output through a 68-ohm series resistor.
- R — Red video channel, TTL-level digital output through a 68-ohm series resistor.
- B — Blue video channel, TTL-level digital output through a 68-ohm series resistor.
References
- ZX Spectrum 128 Service Manual — Amstrad PLC