The “Ground” switch is kinda misleading. Since the amp was designed and built before power mains had a ground (three prong plugs), the chassis is connected, through a capacitor (called the cap of death), to one of the two power lines. Switching the “Ground” switch switches between which of the power lines the chassis is connected to. The idea is that if your amp was humming, switch to the other power line to stop the hum. However, if the cap of death goes bad and shorts, you now have a “hot” chassis and can get electrocuted if you touch it and something else that is not grounded properly. Hence the name “cap of death”. It is highly recommended (and does not affect the collectability of the amp) to get it converted to a 3 prong plug, and have the chassis grounded properly. I just acquired a ’67 Bandmaster, and that was the first thing I did to it. First thing I did to my ’71 Univox bass amp, too. As a side note, the Bandmaster I got… Someone had taken a can of black spray paint to the whole head, faceplate, knobs, grill cloth and all. Even got paint on the tubes and covers. I have got it mostly cleaned up and am tracking down new grill cloth. What a horrible thing to do. Well, at least the pawn shop didn’t know what it was (because it was all ugly black) and I got it reeeeeal cheap. Works and sounds great.

There is a switch for the ground behind the amp, do I need to turn it on? and does it have to be to the left or to the right? and does anyone know if there is a owners manual somewhere for this?

My BM has black labeled Utahs. Haven’t been able to place the year… 64/5 maybe?