Like a few other sets of this era, it uses series heater-chained valves connected to a high voltage secondary winding of the mains transformer, one end of which is connected to chassis. It did provide the makers an option to offer the AC/DC version of the same set sans transformer but using exactly the same valves and a mains dropper resistor. However, unlike the AC/DC variant the AC-only set will continue to work with blown scale lamps because they are powered from a separate part of the heater secondary winding. The other thing that strikes me is it is a vast cabinet in comparison to what's inside it! Cheers, Jerry. Oops, silly me, just spotted R28 that bypasses the scale lamps on the AC/DC variant
