Use the Spectrum 128 style menu below to navigate to the various sections detailing the SCART cable.
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| Introduction |
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The Spectrum 128 improves upon the display quality provided by the 48K Spectrum by having a dedicated socket that outputs both composite video and RGB signals. The composite video output measures 1.2V pk-pk at 75 ohm and is suitable for direct connection to the VIDEO IN pin of a TV's SCART socket. The Spectrum 128 also provides RGB outputs at TTL level. However, since they are TTL signals they are either at 0V for no colour or 5V for colour on. As a result, the two shades of each colour available from the Spectrum 128 are not generated. To overcome this drawback, the Spectrum 128 outputs another TTL signal that indicates whether the colour being output should be shown at bright or normal intensity. Keeping the BRIGHT signal separate from the red, green and blue components allows the Spectrum 128 to drive a monitor that accepts TTL level RGB inputs, albeit with a loss of the two shades of each colour.
The Spectrum 128 was never designed to drive a SCART socket and as a result does not output signals that are ideal for the purpose. It is possible to convert these into suitable signals but it requires significant circuitry and connection to a power supply. However, a decent picture can often be achieved using a cable containing just a small amount of 'passive' circuitry, although this does introduce some limitations. Using this approach, care must be taken not to draw too much current else overheating (and potentially damage) can occur to the ULA inside the Spectrum 128. This website presents a design for a 'passive' SCART cable for use with the Spectrum 128, along with full design calculations. However, it is not guaranteed not to cause damage to the Spectrum 128 and so you are encouraged to scrutinise all calculations. Should you build a cable using the design presented then you do so at your own risk.
The Spectrum +2 is functionally very similar to the Spectrum 128. Amstrad kept the same style of monitor socket but made subtle changes to the circuitry driving it. The Spectrum +2's PCB contains three links that configure the signals output by the monitor socket, and these allow a similar pinout to that of the Spectrum 128 (the default setting) or to output alternate signals such as audio and power. In either configuration, there is also circuitry to internally combine the BRIGHT signal with the colour signals, thereby allowing the Spectrum +2 to be used with both analogue input and digital input monitors. When used with a TTL monitor, both normal and bright colour intensity shades would appear at the same level, thereby resulting in compatibility with the Spectrum 128. However, a SCART cable design for use with the Spectrum 128 is not suitable for use with the Spectrum +2. See the Spectrum +2 RGB Differences section for further details.
The Spectrum +2A and +3 also use the same style of monitor socket but the pinout resembles the alternate configuration available from the Spectrum +2. The Spectrum +2A/+3 can be used with either digital input or analogue input monitors, but note that the composite video and BRIGHT signals are now no longer available. Therefore, a SCART cable design for use with the Spectrum 128 or Spectrum +2 is not suitable for use with the Spectrum +2A or +3. See the Spectrum +2A/+3 RGB Differences section for further details.
The Spanish version of the Spectrum 128 has a different monitor socket pinout arrangement than the UK version. Therefore, a SCART cable design for use with the UK Spectrum 128 is not suitable for use with the Spanish Spectrum 128. See the Spanish Spectrum 128 RGB Differences section for further details.
The Sinclair QL also provides a monitor output socket. Since this is very similar to the Spectrum 128 I have also included details about making a SCART lead for this machine. See the Sinclair QL SCART lead wiring section for further details.
It is possible to connect a 16K/48K Spectrum to a TV via SCART using the SPECTRA interface.
