Sinclair ZX80 / ZX81 / Z88 Forums

Putting in Andy’s ULA solved the screen jump issue I was having in hi res games. Nice one Andy!

Original parts left:-

Motherboard - can’t do much about that
6.5 MHz resonator
Case - might try and make a custom one

I still need to get hold of a UHF modulator for less than £20 and put in an ear and mic socket.

Good work.

BTW I’ve got a few RF modulators in my spare parts drawer. Some of them should work fine, the others are broken. If you need one drop me a line.

McKlaud wrote: ↑Tue Nov 20, 2018 12:21 pm Good work.

BTW I’ve got a few RF modulators in my spare parts drawer. Some of them should work fine, the others are broken. If you need one drop me a line.

Go on, send him a broken one. He loves fault finding on this Zeddy

Mark

Hi Mark

Now you can laugh out loud, because Lardo asked me for a faulty unit

1024MAK wrote: ↑Tue Nov 20, 2018 4:21 pm

McKlaud wrote: ↑Tue Nov 20, 2018 12:21 pm Good work.

BTW I’ve got a few RF modulators in my spare parts drawer. Some of them should work fine, the others are broken. If you need one drop me a line.

Go on, send him a broken one. He loves fault finding on this Zeddy

Mark

I aged 5 years in the time it took me to get this one working!

I only need a broken one for the case.

I just got one of these off eBay, possibly from someone on here?


Loving the keyring! Nice bonus.

In place and working but I need to add the switch so I can play with the other ROM options.


ROM options:

Bugged ROM (the earliest official Sinclair ZX81 ROM with mathematical errors)

Standard ROM (the normal Sinclair ZX81 ROM that was fitted to almost all models)

Standing on the Shoulders of Giants ROM (improved 'Standard' ROM by Geoff Wearmouth, 2003)

Husband Forth (The Forth programming language for the ZX81 by David Husband, mid 1980s)

ASZMIT (Assembler ROM)

ZX81x2 (an improved and faster ROM AKA 'Big Bang' from 2018 by Zsolt Gaal)

A most excellent zeddy you have there Lardo.
Just for clarity there is at least one known maths operator bug in the h4th ROM which may or may not be present in your ROM depending on who programmed it. If it come from the German lads then it's probably not present, a thread here for clarity.

viewtopic.php?f=3&t=2632&p=28741&hilit=h4th+bug#p28741


The manual for the Azmic ROM can be found here.

viewtopic.php?f=7&t=1503&hilit=azmic+rom&start=10

Moggy wrote: ↑Fri May 15, 2020 5:55 pm A most excellent zeddy you have there Lardo.
Just for clarity there is at least one known maths operator bug in the h4th ROM which may or may not be present in your ROM depending on who programmed it. If it come from the German lads then it's probably not present, a thread here for clarity.

viewtopic.php?f=3&t=2632&p=28741&hilit=h4th+bug#p28741


The manual for the Azmic ROM can be found here.

viewtopic.php?f=7&t=1503&hilit=azmic+rom&start=10

Thanks for the links Moggy!

Forth up and running.

Soldering the wires to the switch was an absolute nightmare.

Z80 for scale....
My eyesight is nowhere near good enough any more.