This Rudedog designed PCB inspired by a schematic at zigg.net will allow you to replace the insides of a ZX-81 RF modulator with a new PCB that will give your ZX-81 a much better, stable picture on modern televisions.
This item is for the pre-built and tested version of the PCB. You will need some soldering skills to remove the old RF modulator from the ZX-81 PCB, remove the insides of the RF modulator and replace them with this PCB. You will then have to resolder the RF modulator back into your ZX-81.
Moderate soldering skills are required, but full instructions are provided.
Please 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. Instead, contact us for our standard composite video mod PCB.
If you prefer to have it done by us, and have your ZX-81 refurbished at the same time, see this item in our shop instead: Sinclair ZX-81 Refurbish and Video Upgrade