http://www.vintage-radio.com/repair-restore-information/valve_dropper-calcs.html
To make the dial lamp work. Lift the heater connection at the last tube in the series going back to the AC line. (75) Add the dial lamp is series from the lifted heater wire and back to the 75 heater pin. Shunt the dial lamp with a 47 ohm 1 watt resistor and use a 44 light bulb.