Tube Amplifier Post Phase Inverter Master Volume Mod

A friend of mine had an old, sick Marshall JCM800 head which had some issues from sitting in the Florida humidity. Dirty potentiometers, squealing and he didn't like that he had to crank it up to 11 to get distortion. That's where we clean things up a bit and add a phase inverter master volume control.
(Unfortunately, I forgot to add the footage of cleaning the potentiometers with DeOxit, but wow it made a difference!) The Boss HM-2 was a quick fix which I didn't even record. However, the 9V battery connector was shot - totally corroded and a broken GND wire. Simple enough to desolder and pop in a new one. Replacement 9V connector by in Orlando; What an awesome place!