ZX Spectrum Composite Mod Transistor

The Transistor required to modify the ZX Spectrum to output Composite Video is the BC549C Tramsistor. These are available to buy here and hear .

Also you can buy them in bulk from Bangood here: https://www.banggood.com/custlink/DmDEWOPF93


Transistor Video Mod:

1. Pop the lid off the modulator box and de-solder the top end of the resistor that is connected to the jack socket pin.

2. Desolder the modulator’s input and power leads. Make sure the holes in the PCB pads are clear of solder.

3. Bend the transistor’s leads so it can mounted as shown – The flat side of a BC549C transistor body must face the modulator (the pin layout of other transistor types will vary!)


4. Install the transistor and solder the collector and base leads, trimming off the excess on the underside of the board. Please note: Some Spectrum PCBs have exposed tracks running below where the transistor is mounted – make sure these are not shorted by the transistor’s leads!

5. The emitter wire will be too short to pass through the grommet in the modulator body so use a small piece of wire to extend it. It may be easiest to pass this through the grommet, soldering one end to the jack socket and the finally soldering the free end to the transistor’s emitter.

6. Bend the modulator’s original wires over the side of the modulator and clip the lid back on the modulator, trapping the wires.

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