Hello all, I am brand new to the forum and also to audio systems and circuitry in general. I recently picked up a “black-faced” federal signal pa300 unit. It is currently not working and I was hoping I could gain some insight and maybe get it working. I cannot find any wiring/circuitry diagrams for it online so I have turned to forums. Currently I am unsure what is working but I have a wire that is cut so I am hoping someone could tell me where it connects(?). It is the black wire that comes off of the gain/off knob.