A homemade ZX81 keyboard of wood

[Erm]

This is fascinating. It came in a recent ZX81 lot which included 2 ZX81's that I've got going again, one for spares, 3 ram packs and lots of self recorded cassettes of probably obscure German stuff.

The keyboard is mostly made of wood but has some very complicated looking circuitry going on. Perhaps someone more clued up will know what the extra components do? It has a shift lock and buttons named 'REP OFF' and 'REP ON' (with a light for that and a light for 'Break'). The chips involved are a HEF40106BP and a CD4066BCN. Another interesting addition is that the motherboard it was attached to was using transistors as better diodes.

Not shown in the pics is also a separate number pad with 0-9 and A-F keys, obviously to enable quick entering of hex values.

[mrtinb]

REP ON/OFF is most likely repeat on/off.

[Erm]

Yes, but as in you can hold buttons down and they will repeat the keystroke!? That's a new thing for a ZX81. Must have been amazing at the time.

[mrtinb]

As for Break on/off: Being able to disable Space, so it will not send Break, cannot be implemented in hardware alone. As there is no hardware distinction between Space and Break. Here the ZX81 system ROM has to be updated.

E.g. ZXpand can be configured so break is Shift-Space/£ instead, but this is done with the custom system ROM.

P.S. I don’t know if this is the intension of BRK ON/OFF.

[Erm]

I got it working, connected to my ZX81 test motherboard (which happens to also be the one that was originally attached to the keyboard).

The BRK on/off does indeed disable the Space/break button completely. When enabled, the LED is lit. And the REP ON/OFF is brilliant. As suspected, it repeats keystrokes when the buttons are held down (albeit quite slowly - but the shift lock is good as you can press it, then hold down delete to delete text in a less fiddly way). The LED to show REP status doesn't seem to work, but you can turn it on/off with the buttons.

I think this must have been made in the USA because the m/b was an American one with the ground strap on the back and the keyboard has 'Dele' for 'Rubout'. It's actually a very useable keyboard, just a shame the clear lacquer on the keys has yellowed with age.

[Enigmachine]

That looks like the keyboard from a TI 99/4A with extra timer circuitry for repeats & new functions. See TI99 keyboard adaptation for wiring help without the new circuits.

TI99/4A's are more common than Zeddies so why not sacrifice one to do this. O

[Paul]

TI99/4A's are more common than Zeddies so why not sacrifice one to do this. O

Because nothing compares to a real Cherry Keyboard with ZX81 professional printed keycaps.

[Daeve]

Because nothing compares to a real Cherry Keyboard with ZX81 professional printed keycaps.

How do we get hold of one of those, Paul?

[Paul]

They will be available I guess next year in April. Made by the German ZX-TEAM.

[Erm]

I wasn't sure what model the keyboard was from, knew it was a TI. I've popped in on German ebay, not sure if I'm allowed to link here. It's not the prettiest but is an interesting contemporary homemade addition.