The Timex Sinclair 1000 was a sleek and compact machine, and the US counterpart to the more well-known Spectrum ZX-81. Timex may not have come to dominate the computer market, but the machine still has its fans today, with [skidlz] being one of them. That inspired them to craft a new case and keyboard for their beloved machine, putting a slimline twist on the old classic.
The new case finds some economies of size by eliminating the bulky RF modulator in favor of hacking in a cleaner composite out feed. In turn, this enabled the elimination of the channel switch that freed up more room. [skidlz] then designed a simple case using 2D laser-cut parts and dovetail joints, using superglue to assemble the individual pieces into a cohesive whole.
Meanwhile, the keyboard swap is obvious to anyone that ever used one of these things. The original was particularly unpleasant. In order to upgrade, [skidlz] decided to look to the compact Redragon K603 as an inspiration, giving the new build a longer travel and a nicer mechanical feel under one’s fingers.
The final result look great, and files are on Github for the curious. We’ve seen great work from [skidlz] before, too, in the form of this microcassette storage project. Meanwhile, if you’ve been cooking up your own retrocomputing projects, don’t hesitate to let us know!
Awseome! 😃
The ZX81 may not have been as much of an popular toy computer as the C=64,
but it was nice as a microcontroller with keyboard.
It was cheap, small and black! It had many clones and it could be tinkered with.
It was a Z80 breadboard with a bit of extra logic, essentially.
That’s why it was so much more interesting than a Spectrum, I think.
The ZX81 was like a kit that screamed for modification and expansion! 😃
Spectrum ZX81??? The zxspectrum has nothing to do with the Zx81. It was just called the Sinclair zX81. The ZX Spectrum was the sinclair follow up computer after the Zx81
Yup. As an aside, I saw the ‘Rubber keyed wonder’ film about the Spectrum last week – a very interesting watch.
Sinclair made back in time some good design & cheap things like computers & audio stuff, problem is they did not last long because…you cannot make both cheap & durable.
I still have an old ’78 Apple ][ which does not require a new case nor a new keyboard. But it was not cheap !
Me and my 6 working Spectrums (1 x 48k issue2, 1 x 48k plus , 2x 128k +2 1x TC2048 , 1 x TC2068 ) don’t agreed , changed capacitors and a coule of ram chips and wil last onother 40 years. much longer than any new shiny premium iphone or any modern crap produced today.
To be fair, the Timex 1000/ZX81 had a different audience to an Apple II.
The Apple II in its application was like a predecessor to the IBM PC (Apple II was cloned all around globe).
It had been used in school labs, for example.
The Microsoft SoftCard with that Z80 made it a very popular CP/M PC, for example.
The ZX81, by comparison, was aimed at hobbyists that wanted to learn about computers or wanted to tinker with electronics.
It was something you could interact with without having any fear of breaking it.
Because if you did, it meant no existential crysis (it didn’t cost an arm and a leg).
The ZX81 was closer to an KIM-1 learning computer than to the Apple II or Atari 800.
The use of the ubiquitous Z80 processor, the ULA chipset and defective RAM chips (half the bank disabled) made it very affordable.
Interesting: In other countries, the ZX81 had been cloned, too.
However, without use of the special ULA chip.
Engineers had to figure out a way how to implement functionality differently.
And last but not least there’s 3D Monster Maze! 😃
The original game on ZX81 still is the most haunting version, I think.
Playing it on a real b/w monitor or television set is such of an experience!
Cloning a ZX81 without an ULA is quite easy, since the logic design is basically the same than the ZX80 (with the exception of a little change to allow the “slow mode”), which was built only with standard 74xx chips.
Hi, thanks for the info! 🙂
Weren’t there mods for the ZX80 to make it run ZX81 software?
I think I read about this on the internet, but that was 20 years ago!
Yep, there were mods. http://www.fruitcake.plus.com/Sinclair/ZX80/ROMUpgrade/ZX80_SlowModeBoard.htm
Great keys don’t change the sad fact that the ZX81 scans the keyboard at 50Hz, but only registers a key after 2 scans, which means that you need to keep the key down for at least 1/25th of a second for it to register. You won’t type 25 characters per second, nobody does. :P But you will also not hold the keys down for at least 1/25th of a second. So if you try to type fast many keypresses will still not be registered because you held them down for too short o a time.
To fix that, you will have to add some sort of buffering, something that will register the keypress, and present it to the ZX81 for enough time, kind of like a one-shot circuit, a “keypress stretcher” if you like. ;)
Something like scanning at 200Hz (4 times faster), registering a keypress if it was scanned at least twice (debouncing), and then present that keypress for slightly over 1/25th of a second to the ZX81.
That will cause the ZX81 to flawlessly register keys held down for as short as 1/100th of a second, which is probably enough. And if it’s not enough, you can increase the scan rate (but increasing scan rate will decrease the effectiveness of the debouncing trick).
I thought a bit about a circuit using only conventional 74xx logic, but the amount of IC’s was increasing quite fast. You need to compare previous state to current state. I came to at least one 3-bit counter (need to count from 0 to 4), a 3 to 8 line decoder (only 5 lines used), two 8-bit latches, two 4-bit magnitude comparators, two 555’s (one for 200Hz clock, one for 1/25th one-shot pulse), and a few flipflops and AND ports to make the state machine. At least 12 ics.
Or use a microcontroller with 26 gpios and a small program. ;) :) :D You could do it with an 8048, which has 27 gpios. It would be contemporary technology: the 8048 having been released in 1976 (ZX81 is from 1981).
But let’s face it, you would still have been stuck with a limiting 32×22 characters screen. The ZX81 was never meant to be useful beyond introducing people to computing as cheaply as possible. It served that purpose as no other computer ever did. It was meant for people to either outgrow quickly, or to give up quickly. Giving the first group the confidence to shell out serious money for a serious computer, and giving the latter a limit to the amount of money they wasted. Genius. Would probably have been more Genius if Sinclair would also have provided that serious computer for serious money. But in the UK, it was Acorn who ran with that prize (BBC computer and ARMs). ;)