Organ project: volume pedal fixing

13 April 2018

First task on the organ restoration is to fix up the volume expression pedal. At the moment it flops around, with no tension, so if it gets bumped by a wayward foot you get a nasty volume surprise.

I took the back off the organ - easy enough - and removed the pedal. I was expecting something a bit more complex, but in the end all it needed was a few nuts tightened, and it's as good as new.

The speaker is also visible at this point - a 40w speaker, about 10 inches in size.

I was expecting a potentiometer and some sort of gear system to control the volume. Instead, I found a mystery part with yellow wires, and a mystery part with blue wires. What is this magic?

Once I turned on the power, it became obvious. The blue wires are going to a light bulb. The yellow wires are a light dependant resistor...and the pedal moves a bit of metal with a varying hole cut into it. More light is allowed through when the pedal is pushed down, which changes the resistance. Neat.

I also checked out the bass pedal mechanism. It's pretty simple - springs holding the pedals in place, and when you press on them, it shorts out two bits of metal. The whole thing is then connected by a ribbon cable up into the main body.

The cat likes to help whenever I'm working on projects, and he had a ball going through the pedal housing while I had things disassembled.