Sinclair ZX80 / ZX81 / Z88 Forums

Awesome Mark! Thank you once again - adding this to my notebook, and it's something I need to go over again to start to understand. But the system descriptions are fantastic and it was about this that I am truely amazed, not to mention the fact it does what it does whilst juggling display etc. I was...

Hi Mark, Thanks so much for taking the time to write for me such an easy to understand and forgiving starting point to my question! I did have a logic probe which was supposed to include a yellow led to indicate pulsing but it didn't seem to function (I think by it's chirping I could probably have r...

Thanks Mark, I think I ordered one the other day. I notice that other boards online have this capacitor and resistor in this config so maybe it was the case on some boards. Still marveling at the Issue 3 though!

Here is is. I think I got caught our by max resolution. So this is a third board I have. Thanks for the welcome Lardo!

Hi All, Quite new to digital electronics and I'm have trouble telling my highs, from my pulses or my pulse highs! I'm trying to learn from a functioning Issue 3 board, in order to eventually troubleshoot an issue 1. The issue 1 has ULA issues as no clock on pin 14. I have found useful posts on here ...

Hi All, new member here. I have got zx81 bug for the 2nd or 3rd time. As a kid my Dad used to use one. I remember he wrote a program which would output sound to a TV, 'Tunes' I think it was called and it got publihshed in ZX Computing which I am immensely proud of! So following in his footsteps, I'v...