Apple Keyboard II Modification

The first computer my family owned was a Apple Macintosh Performa 550, which died before I was able to revive it (I had played around with the registry too much and killed the OS). The computer was tossed/recycled, but without the keyboard.

I picked it up and kept it at my desk, figuring there'd be a way to hack it to work with USB or something, but it sat for quite some time before I actually looked it up.

I was right, there's an ADB (Apple Desktop Bus) to USB convertor that can be made with a Teensy 2.0, and also a pre-made one by Griffin (which seemed to not work very well). Last month I finally broke down and got the Teensy 2.0, but didn't do anything with it besides grab the 1k ohm resistor that I would need for the mod.

When upgrading Triela to Windows 10, I got bored and decided to work on the mod, first with the wires and resistors. I used 22 AWG wire, and I noticed that the resistor legs were just thin enough to enable sticking in the hole with the wire. It was a lot easier said than done, but I managed to do it with it looking fairly nice.

"Top" and "bottom" of the Teensy 2.0 with the wires and resistor (the shield drain wire is being used for GND, but is hard to see).

After soldering, it looked quite nice.

"Top", "bottom", and the unit ready for the next step.

I then figured out the pins on the keyboard, checked numerous times, and soldered the wires appropriately to some filter/isolation block thing (because it was easier than de-soldering it).

Closeup of the solder-work, board overview, board in its proper location.

I then played around with the casing to see how much free space was left, which was quite a bit, and the location I figured worked just as planned.

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Teensy 2.0 lined up to some pre-existing groove, spacing inside (nothing close enough to short anything), cable plugged into the Teensy (with the ferrite choke being held by the ground strap thing, and the inside view.

I loaded the firmware to the Teensy and got nothing, and trying different firmwares also yielded no results. I checked the pinout again, checked the resistor was across the correct pins, checked the Teensy itself with the LED flash firmware, and then looked closely at the keyboard PCB. I found absolutely nothing visibly wrong.

I then played around with a multimeter and looking at resistances and found there was absolutely no resistance reading between the voltage in and ground pins of the keyboard's microcontroller ("OL" on the display, not a short). From what I kinda remembered from work, there should be some resistance between those pins, but there wasn't anything. Now that I think about it, I don't recall if I changed the resistance reading range or not.

Anyway, I was a bit upset that the microcontroller was dead, since I wouldn't be able to revive the old keyboard. I'll have to check again with my auto-ranging multimeter, but I'm fairly certain the microcontroller's dead. If it is confirmed dead, I'll probably use the Teensy 2.0 for a PS/2 to USB convertor instead.