WARNING - electronics luddite hilariously attempting to explain things below.
Picked up a second hand Casio VP-1 - looks like this:
So its one of these pedals with a hard-wired TRS cable instead of a removeable one.
Issue was that the expression pedal (using it with the EHX pitchfork) works as intended except it doesn't quite go "far enough".
In other words, at heel down its fine (no change in pitch) but in heel up position it only goes 11 or so semi-tones instead of a whole octave. Looked mechanically fine from the inside, nothing restricting or catching. I imagine for most applications you wouldn't notice it really as it would manifest itself as a slight drop in keyboard volume or something.
So inside the wiring was a red and white wire from the cable onto the main pot which is controlled by the treadle, and a ground wire from the cable onto some metal. On the third lug of the pot was a red wire going to the pot controlled by the minimum volume knob, and a ground wire going to the same place as the other ground wire.
OK! So I assumed the minimum volume pot lost some of its juice over the years (this thing is OLD) and seeing as I don't really need a minimum volume, I unsoldered those wires. Now it doesn't work at all. Tried resoldering some of the wires to the control pot but so far no luck.
I'm guessing this is because the minimum volume pot was acting as the resistor that you need in an expression pedal schematic to control the voltage? Of course there is no resistor in the circuit anymore now.
SO - after all that:
1) Is a volume pot losing juice even a thing? Would it do something similar to what it was doing before if that was the case?
2) Assuming I don't care about a minimum volume pot, what's the best way to wire this thing up as a working expression pedal? Will I need more components (ie a resistor) or can I make do with what I have?
Cheers!
