Here's the amplifier removed from the cabinet. Four valves and a couple of transformers (the black things) as well a a big capacitor on top, and the shafts of the volume and tone controls sticking out at the side. You can also see the lamp which tells you the machine is switched on. One idiosyncracy of early BBs is that the lamp actually shines down through a hole in the underside of the cabinet, so all it does is illuminate whatever the BB is standing on. Weird!