Spectrum +2 RGB Differences

The Spectrum +2 also provides a female 8 pin DIN for its monitor socket and the pin-out configuration is shown below.

Spectrum +2 Monitor Socket Pinout
Pin Signal Level
1Composite Video [LK4]75 ohm, 1.2V pk-pk [LK4]
12Va [LK2]
20 Volts DC 0V
3Bright Output [LK7]
Audio Out [LK8]
200mV pk-pk [LK8]
4Composite Sync TTL
5Vertical Sync [LK1] TTL [LK1]
+12V [LK3]
6Green TTL
7Red TTL
8Blue TTL

Links LK1, LK4 and LK7 are the defaults, and provide compatibility with the Spectrum 128.

The internal circuitry of the monitor socket on the Spectrum +2 is shown below.

Spectrum +2 Video Circuitry

The resistors on the red, green, blue, composite sync (CSYNC) and vertical sync (VSYNC) lines are 75 ohms instead of 68 ohms as on the Spectrum 128. The BRIGHT signal is combined with the colour signals internally via 75 ohm resistors and signal diodes. The BRIGHT, composite video (CVBS) and vertical sync signals output to the monitor socket can be reconfigured via links LK2, LK3 and LK8 with AUDIO OUT and two 12V lines. Each 12V line is delivered through a separate 1k resistor, but note that the two 12V lines are not identical.

Although the Spectrum +2 uses 75 ohm resistors rather than 68 ohm resistors, this difference is so minor that the majority of the SCART cable design presented on this website is also directly suitable for use with the Spectrum +2. However, since the Spectrum +2 already includes components to combine the BRIGHT signal with the colour signals there is no need for additional circuitry to do this. Also, since the Spectrum +2 provides a SOUND socket, this can be used instead of the MIC socket as used for the Spectrum 128.

Spectrum +2 SCART Cable Wiring

If link LK3 is closed instead of link LK1 then +12V is output on pin 5 of the monitor socket and can be used to drive the FUNCTION SWITCHING input of the SCART socket. If link LK8 is closed instead of link LK7 then the audio signal is output on pin 3 of the monitor socket and can be used instead of the SOUND socket.