The WR2 from Cossor dates from 1924/5 and is a dull emitter triode with a built-in filament resistance of 8 Ohms. The filament is oxide-coated.
Difficult to see on this exhibit is the red paint at the top that marks it out as for HF use. The WR1 was for AF use. No actual Type designation exists on either type - suggesting that they were selected on test and painted if a good HF response was found.
Cossor had introduced dull emitter replacements for their earlier valves in the form of the W1 and W2. This valve was made to ease the transition from the six volt filament supply for bright emitter sets to the two volt LT supply for the dull emitter valves. The advertising literature stated that when all the bright emitters had been replaced, the screw could be moved to the other threaded hole and the set immediately operated on the more economical two volt accumulators.
The Cossor paper label and on the glass sloping upwards is the etched Cossor name. The resistance
The open centred Cossor base cap.
The remains of the red paint on the glass and the shaped anode within.
The filament voltage adjustment. The screw is currently in the right hand position that connects the pin directly to the filament. Move the screw to the left position and the short is removed and the 8 Ω resistance is in circuit.
The wide glass tube envelope is 28 mm in diameter and, excluding the B4 base pins, is 79 mm tall.
Reference: 1003. Type WR2 was first introduced in 1924. See also1924 adverts.
