First post here, but I thought I should give a bit of a record of what I did in case someone else wants to fix one of these up, and as thanks for all the resources I found here in various threads.
So this keyboard has a bit of a story to it. The year is 1978. Harris has bought out the Sanders computer manufacturing that very year and they are sharing the same facility used for making them until Sanders is fully folded in. Actual terminal logic PCB's all still read Sanders 1977. Sanders up to this point has been using foam and foil capacitive switches in this line while Harris's older stuff was mostly microswitches.
On the outside the keyboard looks mostly the same as the other earlier Sanders IBM terminal clones. After all, these were advertised to be able to speak with just about any main brand mainframe from the era, including Harris's own.
But what Harris did in 1978 was change the keyboard. Outsourcing to Digitran for their new "tactile feel" capacitive leaf design, later advertised as the tactile butterfly. This keyboard is the earliest example I've found of it with a Digitran PCB date of 11/77. Surviving advertisements for the design are early 80's, like this one from 1982.
So I got this thing on a gamble pretty cheap since it looked like fun. It had seen it's full share of forty years of use and had a carpet of dustbunnies half an inch thick under the keys. The keycaps themselves were yellowed from that lovely original teal to a forest green. But all the important electromechanical parts looked basically new under the dust. Little corrosion and less rust.
First thing I did was remove the keyboard module from the thick ABS plastic case.
Then I got to cleaning and figuring out what I would need to bring it back to life. Luckily, it uses a 8x16 row/column design so an xwhatsit Model F controller was the perfect fit. Unluckily, it had an integrated controller, so every last chip resistor and cap had to be desoldered from the board before that could be hooked up.
Here's what the PCB itself looks like with the leafs and controller, minus the nice 1977 intel chip that they were thoughtful enough to use a socket for.
And here is the plunger plate with the stems and springs.
So after desoldering all the controller parts from the keyboard module, I traced out the pads for each row and column on top and bottom of the 2 layer PCB and marked them for hookup to the Model F controller, plus a couple grounds to that nice huge ground plane on the bottom of the board.
Then I got to hooking it all up.
While all this electronic stuff was going on, I was also working on the keyboard from the physical end, and gave some retrobright a go on the keys which are a lovely thick doubleshot ABS. There's some bloom on some of the caps and I haven't gone and repolished them back to normal yet, but they are definitely teal again and all the white bits are white.
The spacebar as the most yellowed and most stubborn of all, still remains slightly darker than the rest, but I was still very impressed with the results, even if they might not last forever.
And so with everything hooked up, it was time for the moment of truth. Firing up xwhatsit's USB capsense utility, I started manually adjusting the voltage threshold until I could get keypresses. At about 250 I was getting them on bottoming out. Cranking it down even further, I kept raising the actuation point until I got it about where it was originally for the keyboard at 158. No ghosting, full NKRO, I was pretty darn happy everything was working as intended.
I then went ahead and mapped out the base layer, haven't got around to what I want for the first function layer yet. Kept everything mostly the same except I made Clear into escape, turned the exclamation point and backtab into the bracket keys, made Programmable Action 1 into Print Screen and PA 2 into numlock, Reset into Ctrl, Enter into Alt and so on.
Can't wait to fully finish cleaning it up, but it's nice to bring something like this back to fully functional life. I have to say, a pretty cool keyboard and fun to type on. After all, I typed this whole post with it.
