greystroke, the transformer like object is most likely a solenoid (like in a doorbell) to generate a noise when keys are pressed.
I should post pictures of my hall effect keyboard with tripleshots here sometime.
I was thinking it looked like a doorbell transformer, couldn't figure out why a keyboard would need one! Took off a couple of the key-switch blanks, looks like watch batteries under each port. Those must be the magnets for each sensor.
Now all I've got to do is figure out an adapter for a 24-wire (I counted...) cable connector, some sort of interface to deal with the undoubtedly custom key codes, and I'll have a state-of-the-art 1987 91-key keyboard. Yeah, this is going to be a project, all right.
Heh!
Edit: Looking up Key Tronic turned up the following Wiki entry;
"In 1978, Key Tronic Corporation introduced keyboards with capacitive-based switches, one of the first keyboard technologies to not use self-contained switches. There was simply a sponge pad with a conductive-coated Mylar plastic sheet on the switch plunger, and two half-moon trace patterns on the printed circuit board below. As the key was depressed, the capacitance between the plunger pad and the patterns on the PCB below changed, which was detected by integrated circuits (IC). These keyboards were claimed to have the same reliability as the other "solid-state switch" keyboards such as inductive and Hall-Effect, but competitive with direct-contact keyboards. "
So,
not Hall-Effect, after all... Hrm. The investigation continues.
