Don’t bother building it yourself! Ready to install, fully assembled and tested.

Detailed installation instructions (PDF) and technical support are included.

Modern TVs will not display a proper picture using the RF modulator output, and thus require a composite video input. These tiny boards fit easily inside the RF modulator box.

The board is a modified version of the zx.zigg.net circuit, and can also be used on the Timex Sinclair 1000 and 1500. Can be installed either inside or outside of the RF modulator case (see pictures) - no need to unsolder the RF modulator or disassemble everything! Just pop off the RF modulator lid, clip a few wires, solder four wires and you’re done. Minimal soldering skills are required.

Works on UK (PAL) or North American (NTSC) models. Works for ZX81 Issue 1 or Issue 3 models, and all TS1000 and TS1500.

The video mod circuit is needed for two reasons:

1. The ZX81, TS1000 and TS1500 as designed output an analog RF signal (UHF or VHF), which can only be displayed on older TVs, or newer TVs that can accept analog signals. Most newer TVs only accept digital RF signals.

2. Even if your modern TV accepts analog RF signals, the signal generated by most ZX81 and TS1000/TS1500 computers do not have a “back porch” included in the signal, so your TV will not be able to set the black level properly. What results is a picture that is washed out, or has very poor contrast, even with the brightness turned all the way up. You might see a murky “K” cursor by adjusting brightness and contrast, but it will be far from usable. Some TVs can’t even display a usable picture with this signal.

The video mod circuit generates a composite video signal which can be fed to the video input of just about every modern TV. This is the yellow center jack on the back of the TV.