keyboard restorations

Forstalling my prophesized doom restoring a janko piano, starting small with the Apple M1242 Adjustable Keyboard from 1992.

  • I’ve taken the caps off and cleaned them with denture tablets/magic eraser. I’m building a “Retrobrite” (UV/hydrogen peroxide) tub to brighten the brominated plastics back to their original color next. The keycaps appear to be PBT and cleaned up nicely after their bath but could stand to get retrobrite as well.

  • The PCBs (three of them) are all in great shape and there might be room to put a BLE microcontroller/battery in this to make it my only bluetooth keyboard as well. Otherwise how am I supposed to draw enough power for the ADB converter from an iPad mini?

  • The switches are white Alps SKFS (low profile) “tactile” but feature a clickbar and are more akin to a modern Kailh Pink, Jade, or Navy. They’re in astonishingly good shape and cleaning up with aerosol anhydrous alcohol sprayed into each cavity before flushing them. They’re not to my taste but I don’t want to disassemble/lube them or cannibalize another vintage Alps board to replace them.

  • There’s pinging from the bottom plate, an unapologetic piece of barely-finished steel. I’m going to get a material to cover it because it’s too big and structurally integral to replace with a printed part. Looking into mass loaded vinyl, dynamat (tough to cut), silicone, or foam. With boards that have high-profile cases I usually cast some quick-cure silicone to make a damper that presses against the back of the PCB but I’m not sure that’s an option here. Could possibly print molds to cast them but the clearance under each “half” is very slim.


Reading up on the switches.

These are very, very non-standard Alps. The Deskthority wiki lists only three products that ever used them - this keyboard, a laptop, and a keypad from the OEM.

They use four pins, two of which appear to be electrically superfluous and in lieu of feet/prongs for stability. The traces on the PCB are incredibly weird because the dummy pins are connected to each other.

However, unlike MX switches, you can open them without desoldering them. This is good news because the springs are god awful.

So next I’m going to use calipers to take measurements and see about making an switch-opening tool to print so the dozen or so people still trying to use this particular board can tilt at windmills with me.


Switch opener was too much work when opening the switches is very easy using a precision flathead screwdriver.

Lubricated one switch with PTFE oil and the results are… fine? No longer sibilant but not to my taste. Alternating lubricated, then unlubricated.

For reference, here’s my usual keyboard with Kailh Creams.

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