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psteichen
December 22nd, 2014, 07:40 PM
I'm in the process of restoring a Sperry UTS 20 terminal and keyboard. Or actually just the keyboard, the terminal seems to be working fine, though it doesn't do much without its keyboard. I'm not sure this terminal is old enough to warrant a refurb...the warranty card in the box shows a build date in 1992, so practically brand new! But I happen to have a pile of these things, and I need a terminal to go with my IMSAI 8080 project.

I'm attaching a few photos below. I dismantled the keyboard after having difficulty getting anything but Ls and Gs out of it and discovered some corrosion. If you look in the background you'll see that the contact surfaces on the board are corroded badly in some spots. I'm first wondering what a good corrosion removal solution would be that I can make from household ingredients. I'm just planning to buff off some of the corrosion with a mildly abrasive pad, but some corrosion loosening solution would be handy.

Secondly, and this is where I need everyone's input most. There are little sponge disks stuck on the bottom of each key assembly. The top of the disk has a thin plastic layer with adhesive, to stick to the key assembly. The bottom surface is also a thin plastic disk, but this disk has a very thin layer of metal foil covering its bottom. When the key is depressed the sponge disk touches the contact pads on the board and the metal foil completes the circuit and sends off the signal. The problem is the foil layer has pretty much evaporated entirely from the lower surface of the sponge disks. Only a few have any left, and only L and G have a majority left. Also the sponge layer of all of the sponge disks has lost its sponginess and therefor none of the disks make firm contact anymore. My question is, for those of you who can visualize what I'm describing (and I do have a picture of one of the sponge pads posted below and you can see them in the first picture on the bottom of each key), does anyone sell these pads? The whole keyboard is shot without them, but they are easily replaced. I have about a dozon of these keyboards, and figure I could replace all the pads in around an hour per keyboard. Any advice would be appreciated. Especially if someone knows the official name of these little sponge disks/pads and where to buy some. Thanks.

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psteichen
December 28th, 2014, 10:50 AM
I found this great tutorial: http://www.solivant.com/sol20kbd/

Unfortunately still no source for new ones. I'll also amend my original post to reflect my new understanding of how this capacitance keyboard works.

psteichen
December 28th, 2014, 10:57 AM
Okay for whatever reason I can't edit my first post, but a good explanation of capacitance keyboards can be found here: http://www.sol20.org/keyboard.html