The ZX81 finally gets the keyboard it deserves

Few computers polarize like the Sinclair ZX81. The cut-price micro is at once revered for being so cheap it introduced a generation to computing, and derided for the utterly unpleasant keyboard that made that introduction difficult for many. The latter issue has been addressed – not a moment too soon. A chap named Brian …

[sarusa]

Well...

Isn't that a 'cheat'? I know so many Sinclair fans who consider the terrible keyboard a vital part of the experience because otherwise what was the point of putting up with that? You have to glamourize the membrane keyboard as a key part of the experience, otherwise you'd have to admit it was just terrible shite. By providing this, Swetland basically invalidates half the existence of anyone who played Jet Set Willy, Horace Goes Skiing, Knight Lore, etc. on the completely shite stock keyboard.

(Since I'm not one of those people, I think this is pretty swank)

[laughthisoff]

Re: Well...

"Swetland basically invalidates half the existence of anyone who played Jet Set Willy, Horace Goes Skiing, Knight Lore, etc."

He didn't, as no-one has ever played those games on a ZX81... ;-)

#pedantic

Impressive work and swank indeed. I just need one for my Speccy(s) now...

SB

[Geoff Campbell]

Re: Well...

3D Monster Maze, on the other hand...

GJC

[Andy 68]

Re: Well...

And Frogger.

Laboriously typed in from one of the mags, during lunchtime, while desperately fending off cries of "NERDS!" and malicious attempts to jiggle the power cable.

Andy

[ITMA]

Re: Well...

Not to mention the "wobbly RAM pack" LOL

[Geoff Campbell]

Re: Well...

Yeah, but we showed 'em, in the end, didn't we? Guys? Didn't we?

GJC

[wolfetone]

Re: Well...

I see it like this.

The dead flesh was the "best" for the ZX81 at the time, with a proper keyboard being too expensive. Obviously in later iterations of the Spectrum (I know I know it's not the same) they used a proper keyboard, although it was still a cheap implementation of it.

This project, I think, would've been great if it provided a way of getting the rubber dome keyboard for the ZX81. Meaning you're getting a more modern interpretation of what the ZX81 could've had at the time.

But it's easier to use switches than trying to get rubber domes made up, so at least it makes the thing more usable!

[Spazturtle]

Re: Well...

You could use Topre switches instead which are each individual rubber domes.

[wolfetone]

Re: Well...

Well that'd be a better fit. But because Swetland is a great man and made all of this available on GitHub, we could do it!

But I can't do it. I've not got the time. And no one is more pissed off with that fact than i am.

[big_D]

Re: Well...

The later Spectrums had the same membrane underneath, but plastic keys above, not really a "real" keyboard, but a darned sight better than the old ones.

I had a Kayde external keyboard on my ZX81, ribbon cable fed into the case. Much better than the built-in touch sensitve keyboard.

[Peter Gathercole]

Re: Well...

I took a component Tandy membrane keyboard (bought in one of their 10% off per day sales), opened it, scratched out some of the tracks and painted in the required replacement traces with conductive paint (intended to fix heated rear windscreen traces - also from Tandy) to make my (mostly) home-made ZX81 external keyboard. I put it into a case made from 1mm styrene sheet, with a long ribbon cable, which also included a power switch. The key labels were cut from a photo of a ZX81 from the cover of My Computer (the magazine), stuck on using clear tape.

The circuitry for the keys is a simple rectangular pattern, and there are convenient through-board holes on the board to solder the wires to, no additional circuitry needed (in fact, I don't think that it would be possible to use the I/O port on a ZX81, because of the way that the bus was split by isolating resistors the keyboard was read using Port In from the ULA from the wrong side of the isolating resistors)

Although I disposed of the keyboard about 20 years ago when my home-made power supply (which did not come when bought in kit form) went bang, taking the ZX81 with it, I recently came across and used the conductive paint (ironically to repair a fluid damaged Unicomp Model M), still usable 50 years after I bought it!

[Peter Gathercole]

Re: Well...

Can't do arithmetic late at night. It's only 40 years, not the 50 I said. But still a good while.

[the spectacularly refined chap]

Re: Well...

Custom membrane keyboards are readily available for less than this would have cost with Cherry MXs. Just not from your overpriced gaming tat merchants.

[big_D]

Re: Well...

Not me, I had a Kayde external keyboard for my ZX81.

[John Brown (no body)]

Re: Well...

"fans who consider the terrible keyboard a vital part of the experience"

...and apart from anything else, what was so terrible about it? It was a vast improvement over the terrible ZX80 keyboard :-)

[mikejames]

Re: Well...

And the ZX80 was a vast improvement over the thumb-busting keyboard on the Science of Cambridge Mk14... :-)

[Michael Strorm]

Re: Well...

The comment you're replying to appeared to be confusing the ZX81 with the rubber-keyed ZX Spectrum (hence the references to all those old Spectrum games).

The ZX81- which was the model the article was referring to- *did* come with the same flat, touch-sensitive keyboard design as the original ZX80.

[Andy 73]

How times have changed..

... the keycap set for this keyboard costing nearly as much as the original kit for the whole machine did.

Of course the point regularly missed about the ZX81, Spectrum and other 80's computers was not that the electronics were especially clever (many built on previous designs originating in the 70's), but that industrial design took a sudden leap as people figured out how to get a £1000 computer to cost only £79 pounds. Stuff like the ULA, membrane / dead flesh keyboard and sharing 1K of ram between CPU and display was of course wildly restrictive, but enough to launch tens of thousands of careers.

[A Non e-mouse]

Re: How times have changed..

People slate Sinclair for their terrible quality. But it was the low price that reallly kicked off the home computer boom in the UK.

[Vometia has insomnia. Again.]

Re: How times have changed..

Yep. As much as I really admired the spec, build quality and cleverness of the e.g. Acorn equivalents, £300 for a BBC Model A was out of reach for many people. And while the ZX81's infamous Wobbly RamPak™ was wobbly, it was also affordable.

[mikejames]

Re: How times have changed..

Only if you bought the Sinclair memory pack and ran out of bluetack. I had a 16k Memotech memory pack - it came with cutting-edge velcro...

[hardboiledphil]

Re: How times have changed..

I had the Memotech memory pack as well as the graphics pack.

My uncle built the computer from the kit for me and at a later stage he also fitted a keyboard from a library terminal system as that's what he was working with/installing at the time.

[Stuart Castle]

Re: How times have changed..

I never slated Sinclair for their quality. If you want cheap devices, you have to cut corners, and they did. I do slightly slate them for announcing stuff then delaying it though. With someone like Apple, you can be fairly certain that if they say something will be available in 30 days, it will be available in 30 days. With Sinclair, you could be fairly certain it wouldn't.

It actually made me feel slightly nostalgic that RCL kept missing the delivery dates for the Spectrum Next.

[Elongated Muskrat]

Re: How times have changed..

With someone like Apple, you can be fairly certain that if they say something will be available in 30 days, it will be available in 30 days.

And superseded by the next version in 90 days, and no longer getting OS updates in 180 days...

[Vometia has insomnia. Again.]

Re: How times have changed..

Even ~40 years later I'm still astonished by the cost, tho'. I'd never seen an Apple in the flesh until 1983/84 when I spied one in a computer store with a price tag of £650 for the most basic Apple II, minimum memory and no extras. At the time the price of everything else was either tumbling, or in the case of Acorn they were bundling in more and more stuff on top of a spec that was way ahead of that enormously expensive Apple in every respect. I guess I'm reminded of the (almost) contemporary Stella Artois "reassuringly expensive" ads.

[Dan 55]

Re: How times have changed..

RCL have nothing to do with the Next, thankfully. Things are finally moving forward with the Next.

[David 132]

Re: How times have changed..

Yep. The Next Release 2 (they already shipped the R1 successfully a couple of years ago) is on track to be in backers’ hands in Q3. Delayed due to covid and a worldwide shortage of components, which isn’t something the Next team can fairly be blamed for.

[that one in the corner]

Re: How times have changed..

> With someone like Apple, you can be fairly certain that if they say something will be available in 30 days, it will be available in 30 days.

These days, probably.

Back in the day? Not so perfect (<cough>Apple III<cough/> <cough>a working one<cough/>)

[Michael Strorm]

Re: How times have changed..

You forget that prices have gone up approaching five times since 1981 (i.e. the original release date of the ZX81).

The ZX81 was still very cheap compared to other computers, but £79 then would have been over £300 today.

And the ZX81 was cheap *because* it didn't include a real keyboard with all those separate, hard-to-manufacture bits. If it had, the additional cost of a mechanical keyboard would likely have been more- even in real terms- than a good mechanical keyboard today (e.g. this model was £40 in 1982, over £160 in today's money.

[42656e4d203239]

A certain engineer of my acquaintence

now specialising in Video transmission hardware and Software (If he is reading this, which is possible, he will know who he is..) once saved a ZX-81 from the bin by rewiring an Acorn Atom keyboard to work appropriately for the ZX-81. He also cut up the old keyboard for the keycaps. The franken machine lasted quite a while.

Here is a pint to that man and another to the current re-builder of the ZX 81 dream!

[J.G.Harston]

Re: A certain engineer of my acquaintence

I did exactly that for my Spectrum! :)

[John Brown (no body)]

Re: A certain engineer of my acquaintence

"I did exactly that for my Spectrum! :)"

Yes, back then they mostly used a simple polled matrix layout, which also made in incredibly simply to make a custom gaming keyboard working in parallel with the main keyboard. In my case, the four arrow keys laid out the way I wanted them, a fire button under each thumb with a switch to use them as a single switch or as a pair for those games with two fire keys/jump etc and more keys in the middle to be left/right/fire/hyperspace for asteroids-like layouts. All done with 2.5mm jack plugs on leads to customise the layout in a sort of "hardware programmable" way. No messing with micro-controllers. emulation or other "complicated stuff. Just a ribbon cable from the internals to a socket on the outside for the custom keyboard to plug in when needed. Didn't even need to power down to plug it in or remove it. And it still works today :-)

[FirstTangoInParis]

Re: A certain engineer of my acquaintence

Is this the Acorn Atom keyboard that had chips in sockets on the reverse side? A friend of mine said every now and then he had to push the chips back into their sockets!

[andy gibson]

Nothing new

Plenty of add on keyboards around BITD

https://www.timexsinclair.com/blog/keyboards-and-keyboard-accessories-for-the-zx81-and-ts1000/

[s. pam]

I saw a running one 3 days ago

the chap who works on our 1973 TR 6 has one in his office and a spare. both still work, he showed it playing Pong just the other day!

[Will Godfrey]

Never actually owned a ZX81...

However it was this that started me on the slippery slope (for which there is no cure).

A friend had one that died for no apparent reason, and asked me to fix it as "You know transistor things". It was actually a very simple repair. There's a primitive switch-mode 5V regulator with the drive transistor sweating at the limit of it's rating. It had failed, so I replaced it with a slightly beefier one, and fitted a minimal heatsink for it (not a lot of room in there).

My friend had gone on holiday so I had about two weeks to play with it.

P.S. The first computer I owned was a BBC model B

[David 132]

Re: Never actually owned a ZX81...

> with the drive transistor sweating at the limit of it's rating

Probably, knowing Sir Clive, because he had been offered a job-lot of the underspecced ones for a penny-per-thousand cheaper than the uprated transistors!

[steelpillow]

Back in the day...

...there were a plethora of custom cases, keyboards, PSUs, wobbly-ram-pack fixes and the like flooding the market. I nearly went into production with my own, but the competition was too fierce. It's good to see the tradition is still alive, though.

[Elongated Muskrat]

*twitches*

Is the slope on the bottom row in the opposite direction to the slope on the top set? Every keyboard I have ever used (well, ones with proper keys on them) has the slope on the keys in the same direction on all the rows.

What is this, a keyboard for ANTS?

[ChrisC]

Re: *twitches*

From that angle, it looks like it's trying to replicate the concave-ness you'd get with some keyboards back then. We had some odd greenscreen data access terminals dotted around uni when I started there in the early 90's, which looked like rejects from a low-budget 70's sci-fi series, and which had THE most hideous to use keyboard in part thanks to it having such a curve to it. Honestly, given the choice between that or a stock ZX-81 keyboard, I'd have chosen the latter every time...

[Vometia has insomnia. Again.]

Re: *twitches*

I guess it depends; I always preferred concave keyboards, so from more modern offerings I like IBM/Unicomp Model Ms or Cherry MX switches with SA keycaps on them, and one of the things I disliked about my Dragon's keyboard is that it wasn't concave (though it was still stepped); which incidentally felt exactly the same as the BBC's keyboard (at least the ones with the Futaba switches) in spite of what the snobs used to claim. Some people hate concave stuff, though, which is why the e.g. DCS family for Cherry remains so popular, as much as I may not understand it.

[John Brown (no body)]

Re: *twitches*

"I always preferred concave keyboards,"

Same here. For those not aware, the idea is to make each row of keys feel at the same relative angle of incidence from the fingertips based on the home keys, ASDF/JKL: thus minimising finger movement, angle changes and probably RSI. Most modern keyboards give me more strain or tiredness more quickly, and that's even worse with a flat laptop keyboard and even some desktop keyboards which are designed just like laptops nowadays.

[that one in the corner]

Re: *twitches*

> it looks like it's trying to replicate the concave-ness you'd get with some keyboards back then.

And the concave keyboards you can still get, using shaped keycaps and/or a curved backplate (the later for the really posh).

Personally, I love the concave keyboard: hanging over the home row, flexing the fingers mostly with the middle joint and the ends move in an arc that matches the curve of the keyboard.

But as I've said before, all my workaday keyboards are 30 plus years old juggernauts - whilst the more portable (!) newer mechanical jobbie to make the laptop usable is all weird and stepped rather curved. Shudder.

[Vometia has insomnia. Again.]

Re: *twitches*

One of my all time favourites has to be the huge and very heavy keyboard attached to an IBM 5250(? I think; the older twinax thing, anyway). Just in case there was any risk of you not hearing it going clunkity-clunk from the beam-springs, which were already loud enough, it had a floor-shaking solenoid too. Daft layout but other than that it was lovely to use. And back in the day, one of those fugly terminals would probably cost more than your car...

[spold]

Upgrade time.

I guess I will have to upgrade my doorstop.

They are all spoiled anyway since they obviously never had an MK14 :-)

[ThomH]

It should also work on a ZX80 and a 48kb ZX Spectrum then?

Since all three have the same basic layout and underlying physical membrane, connected to the data and address buses in exactly the same way, and correspondingly can be read by exactly the same code to get exactly the same alphanumerics — beyond port FE the top 8 bits of the address are used to enable or disable any of the eight keyboard lines, and the low five bits indicate pressed-or-not per key.

[arielnh56]

Re: It should also work on a ZX80 and a 48kb ZX Spectrum then?

The ZX80 keyboard is on the same PCB as the machine so there is no separate keyboard connector. You have to cut the board in half with a hacksaw and then run like 30 little wires between the traces on the board and the external keyboard. As I remember....

[Persona]

Well deserved

The ZX81 did have the keyboard it deserved. A cheap and nasty one that saved every penny to keep the cost down so we could afford it.

There were amazing tricks done to keep the cost low. The most relevant being I believe that the upper address lines were actually used to scan the keyboard matrix for key presses, presumably by the program jumping to a high address then back to a low one to pull the address line high.

[Andy 73]

Re: Well deserved

The Z80 has an IN instruction that puts an address on the address bus, and reads the data bus, so you can do

LD BC, 0FEFF <- 16 bit adddress

IN A, (C)

that puts A7 low, so the set of keys on the A7 line can each (potentially) pull their output low. A set of diodes and a buffer is all you need to read the keys - pennies for the whole arrangement. The keyboard had 8 'rows' of 5 keys. A side effect is that you can pull all 8 address lines low and test for *any* key being pressed.

I've recently designed a new Z80 machine (MicroBeast) that uses this same technique, but with nicer tactile switches to make the keyboard a bit more pleasant to type on. The horrified looks from the (twenty years younger) engineers I explained the circuit to were worth it.

[John Brown (no body)]

Re: Well deserved

Keyboard "de-bounce" routines. Not sure if any of the Sinclair line ever suffered that, but there were a few early home computers that scanned they keyboard in the assumption that the key contacts were perfect and commonly resulted in multiple detections for a single key press. Later version would fix this is ROM, but early versions often needed the de-bounce program loaded before doing anything else on it :-)

[jdiebdhidbsusbvwbsidnsoskebid]

Re: Well deserved

I don't ever recall the ZX81 suffering from switch bouncing. Mainly I suspect because the time it took to refresh the line of text you were typing was sufficiently long, before the keyboard would respond again. There was no such thing as a keyboard buffer.

I remember if you were typing in a line that was more than a couple of rows on the screen, the line refresh meant it could be several seconds between each key press.

[Pierre 1970]

Wooden keyboard

As a teenager, after three broken membranes of a ZX Spectrum clone, I'd decided (and of course due to the lack of budget) to construct my own wooden keyboard made of wood, a bunch of screws and a sheet of bronze in order to make the key contacts.

Worked like a charm except for an strange flickering of my black and white TV set. At that moment I didn't know too much about electronics, filters, capacitors and things like that.

As an extra embellishment I made two DB9 ports connected in parallel with certain keys of the matrix in order to resembled a Cursor joystick and connect an old Atari joytick to it.

Unluckily I've lost it and have no photos.... I sincerely hope that as a last homage it made part of a barbecue in my parents house.

Andrés

PS: Since I'm from Argentina, the barbecue is the correct way to incinerate old memories :-)

[Boris the Cockroach]

ZX81.... the memorys

have gone finally..... wobbled once too often me thinks

They were great little machines, cost naff all compared to the computers of the era... £600 for an apple 2 but that little membrane keyboard loathed by everyone survived 2 teenaged boys fighting over it and with it until dad hid the PSU at 9pm sharp.

So it was'nt all bad and taught me a shed load about howto program the most bang for 1K of memory which stood me in good stead when entering the jobs market.

As for after market keyboards , always lusted after the memotech stuff since it was well desgned and didnt wobble either.... but things moved on and you can all fight me over this one.

I got the best computer keyboard ever with the memotech mtx512 , even now its far far superior to anything on the market... just a shame I need to figure out a way to interface it to the crap plastic keyboard I'm typing on now.

[petef]

For me the worst aspect of the ZX81 membrane keyboard was that your fingers moved a bit leading to you pushing at dead space and then being eaten by Rex. We mitigated that somewhat by taping things over the keys but that only improved the action marginally. As others have mentioned programs could come to an abrupt end when the 16 KiB (count 'em!) RAM pack perched on the back was breathed on.

[Tron]

The ZX81 was glorious.

The ZX81 and rubber speccy keyboards were quiet. Some of the more expensive ones were very loud. The ZX81 keyboard was also a lot more tea-proof than most. Without these machines, at their price points, I would never have programmed a computer. It would have been something that only the kids of richer families could do, with their BBC Micros. Despite the caveats Uncle Clive should be regarded as a genius. And he was the only guy running a computer company exploring electric vehicles then.

[John Brown (no body)]

Re: The ZX81 was glorious.

"And he was the only guy running a computer company exploring electric vehicles then."

Calling it an "electric vehicle", while technically correct, is touted as one of the prime reasons for it;s failure. In the run up to the unveiling, everyone, especially the press, were expecting some form of car and what was actually presented was a tiny little recumbent tricycle. So the press mostly ridiculed it from launch day onwards. He completely mismanaged the expectations on that one.

[Rtbcomp]

ZX81 Nailed to a Piece of Wood

I used to be a repair centre for Sinclair and Amstrad and I had a ZX80 and ZX81 which I used for testing chips &c. These computers were connected to a keyboard I purloined from an MDS Data Recorder when I worked for them. It consisted of magnet-operated reed switches which I rewired to the same configuration of the Sincalir membrane keyboards.

When I gave up that business I put them on Ebay under the title "ZX81 Nailed to a Piece of Wood", and its ghost still haunts the ether (Google the title).

http://www.sinclairlair.co.uk/z80_zx81_wood_news.htm

[STrRedWolf]

Still a crap layout.

Well, it's better to type on... but you still don't have a good space bar on it.

...unless you got extra fingers and a thumb on both sides of your hands.

Glad we switched to the C64 early.

[jdiebdhidbsusbvwbsidnsoskebid]

Re: Still a crap layout.

I had a 3rd party keyboard with full keys and a space/break bar at the time and I secretly felt like I was somehow cheating.

I can't remember who it was made by but it was a metal case with the original ZX81 innards inside, and a lot bigger than the original plastic case. It looked like a C64 but without the round corners and made out of bent sheet metal. The flat back made the stock Sinclair ram pack less wobbly though. It had a metal U bracket to secure it.