Sinclair ZX80 / ZX81 / Z88 Forums

Hello folks,

I haven't forgotten about this, I had the rug pulled from under me, house wise, so I'm spending all my spare time looking for a place to live for me and my dinosaurs. I'd forgotten how much fun this isn't!

Ah OK, I had no idea that a hardware mod was needed. I've been puzzled by the hi-res stuff ever since I saw 'forty niner' and while I had a 32K '81 on the bench I thought I'd give it a go. In one of those forum postings you link to I note that the DIY internal 16K mod is hi-res capable so I'll dig o...

Tonight's tinkering shows I may have a RAM issue, but where? Traditional games load (3D Monster Maze, obvs) but hi-res stuff and demos choke at some point. Not sure what's going on here. frenchFranken81-401.jpg frenchFranken81-402.jpg frenchFranken81-403.jpg frenchFranken81-406.jpg frenchFranken81-4...

It seems to be impossible to find any info about the fast loader just because the words aren't unique enough. It's been a while since I flexed my ZXBASIC muscles but maybe I can copy the ROM into RAM since there's 32K to play with?

OK, keyboard fixed. IT LIVES! :lol: Took an hour or so to replace the disintegrated discs with the new ones along with cleaning sticky keys. All keys mapped as you would expect, even the REPT key works. FUNC is called by pressing BRK and RETURN at the same time, that took some finding. I still need ...

My new discs turned up while I was on holiday so I should get them tomorrow, then I can rebuild the keyboard and explore the FLM using the earlier program you posted, cheers! (I only became aware the Lisa used Keytronic pads a few years ago, fortunately my main machine still works but I do now wonde...

OK, I've discovered why the keyboard doesn't work :roll: Keytronic conductive pads, and they've totally disintegrated to the point of losing the foil coating on the bottom. So! Do I invest in a sheet of foil, spend ages finding just the right foam and mylar, gluing it all together then punching pads...

YAY! OK, so the little board is doing Something Bad to the picture. Without it I get not only a prompt but random keypresses coming from the Keytronics keyboard :mrgreen: Would it help anyone if I drew out a schematic? This means the RAM boards are OK which was a worry. At power up I can see the usu...

Thanks for that Mark, The little board is fed directly from pin 16 of the ULA then the output goes straight to the modulator input so that sounds more like a back porch generator. I've already stripped the extras off the board so tonight I'll hook up straight to the modulator and see what I get. The...

After trying many CRT TVs and getting the same picture I went for broke and plugged it into my big LCD TV that's allegedly multi-format.

Same picture.

Time for a stripdown to take it back to a stock board with Sinclair ROM to make sure I'm not going nuts