Here are three pictures of the Zeddy that I fitted with the ULA replacement module.

I was using two "dead" ZX81's and working out the causes of the failures on each. Both had been "played with" by someone before I got my hands on them, as some of the pins on the ROM's and one of the ULA's were bent. Both now work. In the end, the faults were due to one defective ULA, an incorrectly fitted ROM and a faulty modulator.

http://www.sellmyretro.com/offer/details...8FITTED%29-1984