The TEA 2000 integrated circuit is responsible for PAL enconding the RGB signal from the ZX Spectrum 128K/+2/+3 ULA. This IC is rather sensitive to electrostatic discharges, and hence, it can suffer damage. Besides, it can become very hot.

I came across a Spectrum +2A, with an issue number I haven't seen before, issue 4. This Spectrum had a number of faults that could easily be solved, but one remained: although the RGB output worked fine, the composite signal obtained at the input of the RF modulator didn't carry color. A faulty TEA200 was the culprit.

Becoming a rare IC, I studied the possibility of replcing it with a modern IC that could carry the same task: get a RGB signal plus sync, and give a composite PAL signal. The Analog Devices AD722 came to help.