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Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment.

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Old 17th May 2021, 1:58 pm   #1
ortek_service
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Default Vintage ASCII-Encoded Keyboard projects - Using standard logic IC's / just +5V

I've not seen these ones I've just found, mentioned here recently.
And I thought they might be of interest, where you want a period-design to work with the older pre-80's computers that often required these (maybe like several classics, here: http://bytecollector.com/my_collection.htm )
- Rather than just using a more modern microcontroller & developing some firmware or modifying the computer's firmware, to directly do the scanning (so no longer ASCII-output) such as: https://abzman2k.wordpress.com/2020/...board-project/

This 63-key one was sold by Radio-shack, where they supplied just the blank PCB with instructions (and the rather less common 74H103 dual Flip-Flop, that Radio-Shack didn't stock). As well as selling a complete keyboard switch-assembly for it - Although presumably only in the USA etc. as I don't recall this being in the UK Tandy's rather more limited range.

http://bytecollector.com/archive/dig...s_keyboard.pdf - Website no longer maintained, so may eventually disappear, but also here: https://manualzz.com/download/860233 / https://manualzz.com/doc/860233/radi...ruction-manual

With some images / mentions of it of it here: http://vdgtricks.blogspot.com/2014/01/all-keyed-up.html and
https://atariage.com/forums/topic/31...1422-keyboard/
(but some website links may no longer work, like http://www.swtpc.com/mholley/Apple/Apple_1.htm)

It does draw quite a bit of current (nearly 0.5A), but it does use many logic IC's
- Although might be cheaper than some of the now getting rare custom Keyboard controllers IC's (especially +5V only ones)


And here is a much-simpler 48-key Popular Electronics (USA) 1974-Apr project, using just 2 buffer IC's (+ a few transistors, and quite a few diodes): https://www.tinaja.com/glib/pop_elec...rd%20_4_74.pdf / http://rw6hrm.qrz.ru/pdf/asciikbd.pdf
(Unfortunately, this website no longer exists http://www.swtpc.com/mholley/Popular...PE_Apr1974.htm )


Of course the hardest part may still be finding a suitable keyboard switch assembly / correct keytops for any replacement switches to be used. And if used with an existing matrix-assembly, on a PCB, then matrix may not be the right-arrangement to be compatibly with fixed-logic without a ROM code lookup table.

Last edited by ortek_service; 17th May 2021 at 2:23 pm.
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Old 17th May 2021, 5:00 pm   #2
Timbucus
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Default Re: Vintage ASCII-Encoded Keyboard projects - Using standard logic IC's / just +5V

Nice find on the TTL only encoder - could be an interesting PCB reproduction.

I have done one with the PIC to us a Dragon 32 keyboard but, decided it was too risky to announce as people would start stripping Dragon's!

You are correct I am not sure I remember seeing the Archer keyboard in Tandy UK but, they do appear at a fairly high price on the bay from time to time.

From the project Ian and I have just completed the Keys, Board Layout and especially the keycaps add incredible complexity and cost. The biggest problem is getting non sculpted keys so you can juggle where they are and of course unless the ( is on the 8 it will never look authentic!
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Old 17th May 2021, 9:52 pm   #3
ortek_service
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Default Re: Vintage ASCII-Encoded Keyboard projects - Using standard logic IC's / just +5V

Yes, the Radio-Shack instructions do give the full double-sided PCB layout
- But scale is probably unknown, and has everything on one drawing, so would need to re-capture on KiCad etc. Although unless pin-out compatible switches were found, it would need updating for current switches.

I do know someone who's had to sacrifice the odd BBC Computer and Atom Keyboards, in order to re-create even rarer Acorn System keyboards. Although the remains of those were all resold to other Acorn enthusiasts to help resurrect other ones.
And he has also done a version using the rather less desirable Electron (Although old BBC Computers were also very cheap and not sought-after until last few years, so maybe these might also become future classics).

But if you've got many incomplete computers spare, that would cost much-more than a complete one to obtain everything to restore, then taking the keyboard from these is probably OK - And could always restore it back again into those at a future date, if all spare bits are kept.
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