The ZX81 Composite video PCB replaces the RF modulator in the ZX81 which will give you a clearer and more stable picture on modern TV's
This design is based off the schematics from zigg.net which have been around for many years and is tried and tested.
To fit the PCB requires some soldering skills. Do not attempt this if you are not comfortable soldering. You risk damaging the ZX81 if you are not proficient in soldering.
Installation: (See pictures for more details)
(Cables are not included)
- Remove the lid from RF Module
- Desolder (or cut) the resistor connected to the RF output pin.
- Cut the 5V wire from the motherboard to the RF Module
- Cut the input wire from the motherboard to the RF Module
- Solder cable from GND pin on the PCB to the GND track on the ZX81
- Solder cable from 5V pin on the PCB to the 5V wire on the ZX81 (On the motherboard, not on the RF Module)
- Solder cable from the IN pin on the PCB to the input wire on the ZX81 (On the motherboard, not on the RF Module)
- Solder cable from the OUT pin on the PCB to the RF output pin on the RF Module.
Note: This backporch mod is not required for ZX81’s with a newer ULA or ULA replacement like the VLA81 that already produces a backporch signal.
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