ZX81 toZX80 conversion.

[Moggy]

Having acquired a Zeddy from Lardo, I was intending to turn it into a ZX80 as cheaply as possible, however it was far too good to butcher as Lardo had re-done the logo, fitted new feet etc and seeing it has an original working membrane (far better and much softer key press in use than the replacements just lousy ribbons) I thought I'd keep it for when I want to relive a few memories.

So I dug out a scrap case and rather than fork out for paint which I don't posses, I covered the top case with white fabric tape. the lower case I left as is seeing as it is a ZX80/81 hybrid. I also did the same to a Memotech RAM pack. The logos are from a PDF taken from the forum.

The innards.

The ROM image I burnt to a 2764 EPROM, fitted the four resistors to the CPU required to stop the NMI from running when booted, the board already had one of Karl's video boards fitted so I added a button switch to toggle between normal/inverse display and border.

The keyboard in the picture I superimposed as I'm currently awaiting a "clicky" from Karl.

Just thought it might be of interest.

[Spinnetti]

I made up a bunch of replica zx80 cases.... Was only planning to do 2 of them but got a little OCD so have a bunch of every slightly so different versions lol. If we were on the same side of the pond, would be a good option, though I like the white zx81 case.

[1024MAK]

@Moggy, it's all white mate

Mark

[Paul]

I can't work those CAD programs but a 3D printed ZX81 top case with the added ZX80 hood would be a funny thing to own

[Paul]

Just thought it might be of interest.

Hi Moggy,
I think it is of interest and as it's still fresh, could you please add some links for interested people to those pdf in the forum and also to the four resistor add-on.
Oldies like you and I know, but there are newbies out there as well

[Moggy]

Just thought it might be of interest.

Hi Moggy,
I think it is of interest and as it's still fresh, could you please add some links for interested people to those pdf in the forum and also to the four resistor add-on.
Oldies like you and I know, but there are newbies out there as well

Yes will do Paul.

The resistor mod by the way came from the German forum and credit is due to them for this modification.


The conversion details from the German ZX forum, in German language obviously but if using google chrome browser it will translate for you or use google translate. Also a link to details on this forum.


https://www.sinclairzxworld.com/viewtop ... x80#p14097

https://forum.tlienhard.com/phpBB3/view ... t=NMI+zx80


Sticker PDF.

[Moggy]

@Moggy, it's all white mate

Mark

[siggi]

You should replace the black stripes by real slots (for better cooling) ..

[Moggy]

I have just the tool for the job!!

[Moggy]

The "clicky" keyboard arrived today and I must say that the inclusion of the two little finger boards for soldering onto the ribbons is a most welcome improvement to this excellent keyboard of which I have half a dozen and I'm not disappointed with them.

For those who may not know, the original keyboards from Pokemon/Karl had just the bare ribbon ends to push fit into the keyboard sockets and in my case I found this quite difficult.

They now come with two small boards with gold fingers on them that once soldered to the ends of the two ribbons, can then be pushed gently into the sockets for a firm grip, so yes a most welcome easy fit solution.

An observation about this conversion is that whilst all my programs load as they should there are problems with those that use the "flicker free" display.
In some cases they don't load at all and those that do either present a blank screen or some kind of display artefact with very few actually being usable.

The conclusion being that anything written for original ZX80 will work, whilst "improved" programs may not.

Anyway well worth the effort I think and very glad I did it.