The 27KU is a half wave rectifier with the two rectifier sections connected in parallel internally. The maximum reservoir capacitor can be up to 60 μF. with a minimum series resistance of 15 Ohms. The heater takes 6.4 V at 0.45 when power is applied between pins 2 and 71040.
Reference 1040 gives the heater as 3.2 Volts whereas 3002 gives the heater as 26.5 Volts at 0.45 Amp. Both give the same base connections.
The twin rectifier sections.
The heaters are a fine insulated coil folded in two and inserted into the cathode tube. Each anode has four points to offer the greatest area for radiating away the generated heat. This construction points to the 26.5 volt heater.
The classic envelope is 44 mm in diameter, and excluding the IO base pins is 109 mm tall.
