Sinclair ZX80 / ZX81 / Z88 Forums

Hi, I have little experience with ZX Spectrum and Argentinian clones that are 99% as the original ZX but none with this russian (I think it's Ukrainian from the early 90's). Its video output is RGB it doesn't have a video encoding circuit. As I don't have any 15khz RGB monitor or SCART TV Ive made a...

Just a thought
The bigger rated (non regulated) PSU at the same load should be delivering a higher voltage. This necessarily will get the linear regulator on ZX81 and the heatsinc hotter. Remember that the 7805 regulator converts the extra voltage over 5v to heat..

Space Invaders by SplinterGU
https://splintergu.itch.io/space-invaders-for-zx81-wrx

I'm using this slotted diag rom: http://blog.retroleum.co.uk/20170918/smart-card-v2/ I cannot access any menu test functions as the initial boot the diag rom auto tests the lower/upper ram. If any ram errors are detected then I cannot proceed any further. The ram faults are always 16K/48K spectrum ...

I'm having a similar problem but with Smart Card V2 ROM Diagnostics v1.40. The RAM tests seem to be reporting bad ram for the 48K model and shows the IC numbers at fault for a 48K spectrum (IC6,IC9,IC18). I have a 128K +2 grey model similar to toastrack board and these have 16 RAM chips starting fr...

Hi, i have this Diagnostic Cartridge with Brendom 's ROM, that works flawlessly with many ZX 48 and clones.. But gives me this result with a perfectly working ZX spectrum 128 6U board.. The +2A / +2B / +3 / +3B have different ROM chip control signals on the edge-connector/expansion port, so hardwar...

Thanks a lot!!

I've just made something similar to a 128 Toastrack. R115 from de AY to mic is originally 10K. In other sites they recommend to use 2.2K or 1.65K I tried 1.5K with insuficient result. then I soldered mounted in parallel another 1K resistor resulting in 600ohm .. Then I raised r35 from the ULA to mic...

Hi, i have this Diagnostic Cartridge with Brendom 's ROM, zxdiag-main.png that works flawlessly with many ZX 48 and clones.. But gives me this result with a perfectly working ZX spectrum 128 6U board.. 20220108_190834.jpg I think you can imagine my cold sweat running at that moment... I just wanted ...

mrtinb wrote: ↑Tue Dec 21, 2021 12:00 pm A google found this. Maybe it's the one.

https://github.com/mcleod-ideafix/zx81putil

Thank you!!