Sinclair ZX80 / ZX81 / Z88 Forums

redhawk668 wrote: ↑Tue Jun 08, 2021 11:01 pm
For the ZX Spectrum 16/48K I designed an s-video board to replace the modulator, to provide dotcrawl free video output.

Welcome on board.

The dot crawl free board sounds interesting.

Thanks Mark. I transplanted my rebuilt zeddy inside and it works a treat. :D (still need to finish the switch on the ROM) Then I decided to put my ‘Spand inside. Nope…. 2D7FF549-AB06-4F0A-AA2D-339AEC1135DE.jpeg Going to hit the PSU. OK. Put back the IO expander and then mount it on that. FBC39433-72...

This is about the sixth design of ZX81 RAM pack that I have seen. Each one uses a different method or different variation of design for obtaining a -5V supply. Some use a transistor oscillator driving an inductor like the Sinclair 16k RAM pack. Some use a CMOS logic chip and capacitors to do it. So...

Erm wrote: ↑Thu Jun 03, 2021 11:58 pm Thanks. Looks good them. Leave it on for an hour, but only if you have the time.

It happily played The Gauntlet for best part of two hours.

Some photos of the inside here viewtopic.php?p=43130#p43130

And a Stonechip Panda 16K RAM pack:


Close up of RAM chip:

Moggy wrote: ↑Fri Jun 04, 2021 2:52 pm Nice Lardo.

I have a soft spot for those Stonechip memory packs, more reliable than Clive's offerings in my opinion.

Having not seen one before I have had two of these in an many weeks! Like buses.

A very nice boxed issue three with RAM pack and learning lab. All working (but not tested the learning lab)!

It has happily run The Gauntlet and Rock Crush with a Chroma81, Memotech Keyboard and ‘Spand plugged in for about 10 mins so seems fine. Happy to soak test for an hour at some point if you want? 7B549848-F744-4CA9-8524-5C87F779F91D.jpeg Hard to believe but the screen is actually white! 687560CB-3391...

Erm wrote: ↑Thu Jun 03, 2021 7:17 pm Yes, ok, thanks.

Does it work?

I will check it out over the weekend. It boots to the K but thats all I know so far.