Lower Keyboard Switches
I lifted the upper manual to take a look at the lower manual. One interesting thing is that the wires from the top row of the upper manual contacts connect to the top row of the lower manual, note for note. When I looked at the schematic, I realized that because this was what triggered the rhythm circuits, the manuals were permanently coupled for that purpose. No real problem–I plan to cut the wires leading from the upper manual at this point and route the wires to the inner case for attachment to the DIN units of the MIDI controller (more on this later).
The lower keyboard was slightly different, but still had an easy way to bypass the resister and diode circuits so that direct on/off switching was possible. Again, the upper contact was a whisker wire on a silver bar.
The alligator clips are connected to where there is a non-resistant on/off switching circuit. This means that a simple jump wire bypassing the diode (located just above the red alligator clip) will let the switch work through the existing wiring.
Here is a shot of the lower keyboard wires coming into the case awaiting snipping and connection to the DINs.
I was nervous about the pedal switches, having heard horror stories that Baldwin pedal contacts involved some sort of black goo. The schematic showed a circuit that included a resistor and biased diodes. The theory was intriguing: the pedal 8′ and 16′ signals were always on but prevented by a diode from proceeding to the various filters and amplifiers. When the pedal was depressed, the switch applied an 11 volt load to the diode, essentially opening it up to allow the signal through. Very ingenious and somewhat Rube Goldbergish (look him up if you haven’t heard of him!). I think it was a way to allow the signal to come on a bit gradually instead of abruptly.
In any event, I don’t need such complexity. I was hoping that I could find an easy way to bypass the existing circuitry to get a simple on/off switch for each pedal note.
Here is the switching assembly with the cover on:
What I labelled “pedal switches” above are actually plastic jacks. The are thin, somewhat brittle, and therefore fragile. I took care when working on this assembly to not bump them against any other parts.
For reference, the jacks are pressed down by felted tabs on the end of the pedals:
Cover taken off:
After the cover came off, I got my first glimpse of how the switches work. There is a whisker wire passing through each jack. When the jack is depressed, the whisker wire contacts a rail.
The alligator clips locate the non-resistant switch points. It looks to be a simple matter of jumping past the resistor below the black clip so that the existing pedal wiring can be used. The red clip is attached to an uninsulated wire that grounds the entire pedal switch assembly.
So, this initial reconnaisance tells me that, with a little work on each contact assembly, I can use the existing wires to send switching signals to the MIDI controller.