hi Mark, the radio connects to the discharge post of the amp-meter so that it indicates the radio current example, with engine off, radio on, you should see the amp-meter needle showing discharge to let you know your battery is draining photo attached from installation guide
the original radio knobs have a set screw, but as old as the radio is, the replacement knobs from even way back in the day were press fit so by now, you might have either kind of knob turn the knob and look for a set screw, if no set screw, it pulls off i took some photos of original knobs i have on hand, i am missing an original dummy spacer that goes behind the tuning knob -stan
