Another newbie question on my new to me 37. The car came with the radio under the seat. The guy I bought it from said he had the radio tested on the bench at a radio shop and it worked. It was mounted back under the seat, but not hooked up. I have a few questions. Am I correct in assuming the grounding is through the body of the box screwed down to the floor? It seems to be grounded OK. When I hook up the power, I get a fairly loud hum and the tubes begin to light up. Is the hum normal or is that a problem. Now as to the knobs. The top knob is the tuner. The bottom knob seems to be the volume control. Is this correct? What is the small center knob, it is turning something inside the radio, but I can't tell what. How do you turn the radio off? I was going to try hooking a speaker up tomorrow and seeing what I get. Does anyone know if it is 4 ohm or 8? Or something else entirely? Any insight would be appreciated. I have the shop manual and some other books, but nothing I have covers the radio. Shawn