Sinclair ZX80 / ZX81 / Z88 Forums

Maybe I have just been unlucky - but also surprised that several google searches have found no-one else with the same issue. My photo of the board has a date stamp of August 2018 but I have only recently been motivated enough to find a fix. I also had to blow a new EEPROM using an Arduino to get the...

Does anyone know why the video output mixer/combiner uses 160 and 750 ohms resistors? I tried 4 different TVs and a composite video to HDMI convertor box and could not get a stable picture. I changed the resistors to 470 and 1k ohms - as used on the Arduino (and probably other!) composite video tuto...

:oops: so shortening the cable did indeed get all of the keys working - thanks for the suggestion. I didn't fancy stripping 13 fiddly wires again but at least it was a nice simple fix. As you say, I'll need to buffer the signals if I want a longer cable. Next the strange video. I'm thinking of start...

Hi, I have been getting my (kit built by me) ZX81 working again in the last couple of months. It has a new sockets for the chips (except the 2114 SRAMs - planning on upgrading to a 16k or 32k SRAM at some point), new Andy ULA and freshly programmed EEPROM. Also a DKtronics replacement keyboard. All ...

Hi

Been lurking in for a bit, trying to get my old 81 working again.
Built from the kit, bought with the earnings from a summer job (well, a bit of the earnings).
It's not quite right yet so will post in the appropriate for a bit of help please.

Regards,
Dave