Sinclair ZX80 / ZX81 / Z88 Forums

Thanks Mark. I got lucky - I bought the last two Traco TSR 1-2450 regulators from retrorevivalshop.co.uk for £15 shipped. Once I have that bad composite mod sorted both machines will be golden.

Great thanks for the info! I have to say the WESPI is an astoundingly good project. Mostly in software, and such an elegantly simple circuit design. Really fantastic. I just can't get over the WiFi config being done on the actual ZX81 also :) I received my replacement keyboards and just tested again...

I have just used my multimeter to measure current draw but putting it in series with the supply current. I touched the tip of the power jack against its rightful contact on the socket (from the side), and used the multimeter to bridge the ground pin to ground on the board by jamming the other probe ...

Fantastic - would this do the job ok? There aren't multiple specs of 555 are there (well apart from Chinese fakes)?
https://www.switchelectronics.co.uk/ne555p-timer-ic

I'll hang fire on an order until you confirm which other components I may need to order.

I was able to successfully use a Toshiba TC55257 which, consulting its datasheet, was sold as an equivalent to the various 62256 chips commonly suggested for this mod. I found it by simply Googling "32KB SRAM DIP-28" I think. There's one left for £1.80 if you're quick! https://www.ebay.co.uk/itm/143...

Funnily enough I grew up in France and one of the things I like about the ZX81's block graphics is how much they resemble the Minitel graphics. And also Teletext I guess. We had the basic Minitel which was free but if you wanted the one Martin's using with the retractable keyboard you needed to pay ...

It's troubling that the seller acted like mine must have been defective when in fact every single one he's sold will be like this. And it even does this with the good ULA. There must be dozens of them out there. Perhaps a lot of his customers buy them with the intention of fitting them at some point...

It doesn't even stick out. That's the beaut. The antenna is on the PCB. The ESP32 is incredible really. £7.50 and it can even run Doom!.

I guess it's when you consider quite how much work is involved to manufacture anything (see the many Spectrum Next blog posts), that it seems so silly to get the lettering wrong. Especially considering how much stuff went right. I mean even the graphic characters must have been very difficult to pri...

The guy did the comparison video I linked this time last year, so AFAIK no one has produced any membranes since then. Anyone who's restoring a ZX81 is very likely to also be a pedant :lol: so I think it's probably best to try and salvage where possible, and only fall back to a reproduction when it's...