The DFA3 is a directly heated output triode. A faint etched Mullard aerial, coil and earth logo is on one side and a type three BBC stamp is on the other side. This dates this exhibit to between 1924 and 1927.
The electrodes are obscured. The paper label says the maximum filament voltage is 6.0 V.
The balloon envelope is 45 mm in diameter, and excluding the B4 base pins is 99 mm tall.
Reference: 1043. Type DFA3 was first introduced in 1925.
Absolute Maximum Operating Conditions¶
Updated May 01, 2013. shape:balloon construction:pinch type:triode age:1920.1930 base:b4 heater:6.0v pins:4 pin:1.a pin:2.g1 pin:3.f pin:4.f