Sinclair ZX80 / ZX81 Forums

While trouble shooting my poorly rebuilt zeddy I did benchmark logic probe tests on a healthy Z80 and ULA:- https://www.sinclairzxworld.com/viewtopic.php?f=7&t=2592&start=130#p32197 In my case it was a dodgy transistor. Not sure which one as I replaced them both. Are you able to chip swap with a wor...

I must admit I have not tried dropping back to BASIC with the double buffering code. It may be that the code upsets some BASIC system variables.

Hi Bruno

I can’t see an attached file?

You could always try very simple double buffering:-

viewtopic.php?f=6&t=2372&p=25375&hilit= ... ing#p26810

Merry Christmas!

Having had a go at this process (e.g. https://www.google.co.uk/amp/s/stiggyblog.wordpress.com/2011/09/04/turbo-loading-zx-spectrum-games-via-iphone/amp/) I managed to get it to work with the original cassette cables that came with my Spectrum but only by very careful placement of the mono jack in a ...

I have applied the floating bus partial implementation mod from here https://spectrumforeveryone.com/technical/performing-the-in-ff-mod-on-a-spectrum-2a-3/ to a spare +3 I have at the moment and it seems to work fine. As a quick aside does anyone know of any games that rely on this behaviour to work...

Fitted the new caps and it certainly reduced the jail bars. It made little difference to the stability of the black however. I tried another identical ULA from a work in progress Spectrum (a 4S) and it made no difference. I also put back the original Z80 (that I removed to make the DIVMMC work) and ...

A kludge fix zeddy is one with the early bugged ROM - it has maths issues. They were sometimes fixed by placing a PCB over the Z80 to skip the unwanted instructions and correct some issues. A photo of one can be found here:- https://www.sinclairzxworld.com/viewtopic.php?f=7&t=2153&start=150#p26265 T...

I ended up getting a couple from here

https://www.retroleum.co.uk/zx-spectrum-chips

Ideal if you only need one or two - no minimum order value surcharges.

If it turns out you need a Z80 see this thread viewtopic.php?f=9&t=3037