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Old 26th Apr 2018, 8:58 am   #28
SiriusHardware
Dekatron
 
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,484
Default Re: MK14 schematic revisions

That was fast! I look forward to seeing a completed machine.

When my MK14 kit arrived I tried everywhere locally for 18-pin sockets and could not find any, at which point my patience ran out and I built it anyway - to this day, it still has a mixture of socketed and not-socketed ICs.

I took a look at that ex-calculator keypad I mentioned - as I recalled the pads for the three 'feet' of each metal dome were broad, smooth and heavily plated but I also noticed that the feet don't actually move or skid when the domes are pressed- instead the shape of the main part of the dome just flips from convex to concave. Anyway, this is of limited interest now that your domes aren't going to fit anyway. To be honest, you had a lucky escape there.

I did go looking at keyswitches such as the Cherry MX series - to my surprise there seems to be some kind of renaissance surrounding PC keyboards with proper mechanical switches, with people custom-building their own keyboards. You can even get a 'sample kit' of the nine or so subtly different versions of Cherry MX series switch (distinguished by the colour of the actuator) so you can try them all out and decide which one you most prefer the feel of.

As to keytops, the way to get those is to buy a full PC keyboard set of keycaps which will obviously include some rectangular and other odd shaped keys you won't want, but will include plenty of the square ones you would need. It doesn't take much searching to find a full blank (unlegended) set of black or grey PC keyboard keytops (designed to fit the Cherry MX series and clones) for very reasonable money.

But anyway: Good luck with finding the ICs you need. If you have trouble finding any let me know and I'll have a hunt around, I do have a few 'original' 74 series ICs, although most of what I have will be 74LS... series.
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