The AZ1 directly heated full wave rectifier is fitted with an eight pin side contact base. These bases were used originally by Philips in Europe and Mullard in the UK for universal valves from the 1930s. Universal meant valves for AC or DC supplies. When the Ct8 base proved unpopular in the UK some of the valves were re-issued on a standard International Octal base. For the AZ1 the re-issue was be the AZ31 with identical electrical characteristics.
It has a 4 Volt filament rated at 1.1 Amp. The maximum anode RMS voltage is 500 Volts. At this anode Voltage the DC current could be up to 60 mA. At 400 Volts on the anode the output could rise to 75 mA and with 300 Volts on the anodes the output current could be 100 mA. The maximum reservoir capacitor had to be no more than 60 µF.
This exhibit arrived with no identification present. The heater was tested and armed with this information the rectifier pictures were scanned for a match. Eventually a precise match was found and in all probability this was made by Philips in Eindhoven.
Face view of the anode. The filament can be seen.
The filament tension spring and the oxide coated tape held in the hook of the spring.
Top view with the right side filament in clear focus.
Here the filament tape can be seen to be very thin. The short length of spring is welded to the central support rod.
The classic envelope is 45 mm in diameter and, excluding the Ct8 base pins, is 99 mm tall.
References: Data-sheet & 1040. Type AZ1 was first introduced in 1936. See also1936 adverts.
