Rebuilding 1230 keypad using 3D printer
In order to fix a 1230 key pad I've had to replace the switches with a different type and create new key caps on a 3D printer. This page documents the process.
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I've gotten a 1230 with a handful of keys not working. Turned out the switches have decayed terribly. The switches have a metal dome and a plastic body with metal wires molded inside. A fairly long plastic key cap sits on top of the switches. The wires were all rusty, some of them have disintegrated completely. In some switches corrosion between the dome and the wires prevented making any contact on press.
The switches need to be removed. I used a soldering iron and a screwdriver to gently pry the switches off. In my experience all went smoothly and I didn't lift a single pad despite the use of a screwdriver.
Even though the board looks pretty disgusting, the corrosion didn't make it under the solder mask. All that was neded was a bit of soap, firm scrub with a brush and an alcohol bath.
Now we need new switches. Unfortunately, I couldn't find compatible ones anymore. They're probably not made anymore. Instead, we'll solder some legs to the regular TS6601H 6x6mm SMD switches. I've used ones with 7.3mm knob, but other lengths will do too.
I've attached three bits of wire to each and bent them downwards gently. If you got cut off legs from THT resistors they'd probably make a perfect kind of wire for this purpose. Don't worry about being too precise, you can adjust the alignments when the switch sits on the board.
Now solder the modded switches to the board. Align the switches firmly, start soldering from the top and then perhaps add a bit of solder from the bottom of the board too. Be careful not to solder on vias -- they sometimes get in the way. In some cases you need to snip an extra leg of the switch off.
With the replacement switches, the original key caps no longer fit and you need new ones. I've made a 3D printable model (File:Tek1230-keycap-cad-stl.zip) of ones that hold firmly to my switches. Print supports enabled and the top face on your hot plate (upside-down). That way the supports will break away nicely and your button will a have smooth front side.
Hopefully the model will be good enough for you -- if not, feel free to modify the OpenSCAD source. If you don't have a 3D printer, pay a visit to friendly folks at your local hackerspace. Bring some bottles of Club Mate and they'll surely be happy to help.
Now put the keycaps on, install the board back and rejoice -- you've fixed your 1230.
Posted on 27 May 2021 on behalf of Lubomir Rintel. Thanks to Lubomir for his hard work in rebuilding the keypad.