Below is a video in which I discuss a pitch bend problem in a Korg Synth MS-10. The main thing is how to look at the schematic and determine what voltages should be present in the circuit.
Where the fun begins is when you don't have the voltage present and you have to figure out why.
Click on the link above and you can view a portion of the schematic...As you can see the + and - 15 volts D.C. are the output of the analog power supply. I isolated the pitch bend assembly so you can see how the voltage is presented to both sides of the pot.
As you turn the pot it gives the desired output voltage that the synth player is looking for to drive other modules on the synth. The customer's problem is that is wasn't working at all. The problem ended up being an oxidation buildup on the molex connector that connects the pot pitch bend assembly to the main board where the power supply components reside.
So it was a simple repair but in the video you can see how I came to this determination and also by studying the schematic.