Sinclair ZX80 / ZX81 / Z88 Forums

I can confirm that it was the ULA chip causing some of the problem. I now have a replacement and your board is working really well.
Cheers Trev

I'm starting to think my ULA chip is faulty. I've been thinking about getting a replacement and a heatsink. I don't think it's anything to do with the CCB board.
I'll try both monitors again soon and I've got a television with a video in socket I'll try that too.
Cheers Trev

I have to apologise as it was my monitor that was playing up. I was using a Kaga green screen and now I'm using my Apple green screen and the picture is clear but missing pixels which I'm guessing is the ULA being a 1981 version. Time to look for a replacement.
Thanks for your help.
Trev.

Yes I did use the jumper. I've wired a switch to it so I can change it without opening the case. The zx81 had a different composite board in it when I got it but it was crudely made so I removed it and put yours in.(it too had a distorted K) I've wired the input to the UK2 pad next to the modulator ...

Hi. I can't seem to get your board to work properly and I'm wondering if I have a faulty ULA chip. I've removed the rf modulator and placed the board in its casing with the output wires going to the tv socket and the supply and input wire coming from the board. I still get a distorted K on the scree...