Sinclair ZX80 / ZX81 / Z88 Forums

Yup. Whoever constructed this particular board in 1982 obviously felt that some of these resistors were completely optional. The vias were completely filled with original solder, so it hadn't been removed - they'd just never fitted it. This resistor is the 8K2 pull-up resistor on the D2 line (which ...

So. The results are in. :) The Spectrum is now working correctly (it was sent to Alex to test the ULA and well.... I couldn't just send it back knowing it didn't work right, could I?!). The first thing I did was do the mandatory modifications in the service manual, which I thought may fix it - but n...

Aha! Thanks for that!

Hi everybody, Another weird ZX81 mod. :) I just opened a ZX81 (shortly to be sold) and found this little daughterboard on the Z80. It's a 74LS27 and a 74LS12 on a printed circuit board attached to the pins of the Z80. It''s a proper board and solder job (the pins are still in the socket). Anyone kno...

Andy's ULA replacement is awesome :) However, it's just not ... original. To most people it doesn't really matter that it's not an original ULA but I personally like to keep things as they were when they came out. Otherwise it's not really a ZX81 any more, it's a modern replacement (after all, the U...

Got some here:
http://www.mutant-caterpillar.co.uk/sho ... ts_id=2901
Any problems, just yell!

Hi, Without a clock signal you will not get anything at all - so it's likely to be the ULA. Are you able to desolder that ULA? It's one of the very early types. If you can't do it I can repair it for you but I'd need to charge £35 for it as it's part of my shop service (£30 + £5 for a nice new ULA -...

Hi everybody, I just got an interesting one in... I knew it was an upgraded ZX80 because of the keyboard overlay, but this one uses SLOW mode and FAST mode too! I wondered why it had ZX81 games with it (including two pre-hi-res Software Farm games and 3D Monster Maze)..... There's a board attached t...

It's normal - these dealers aren't usually interested in shipping by mail because they're interested in volume orders - hence they use couriers. The only exception I know of is utsource.net, which have a minimum 1pc order, so it makes sense for them to use regular mail, the resellers like these norm...

I just received my second batch of 10 ULAs - this time from Hong Kong. Interestingly, these ones look different to the others. They're also cleaner and unused (the others I think were unused but had stains on them). Even more interestingly, instead of 80% being dead, this time 80% are alive. These a...