The WD-11 vacuum tube, a triode, was introduced by the Westinghouse Electric corporation in 1922 for their Aeriola RF model radio and found use in other contemporary regenerative receivers (used as a detector-amplifier) including the Regenoflex and Radiola series.
Contents
The WD11 and "RCA-11" (and later simply named "11" by RCA and Philips/Miniwatt) have the following characteristics:
Drawbacks
The WD-11's design was somewhat ill thought out, when the filament burns out it has a tendency to contact the plate, feeding high voltages back through the heater circuitry. It was replaced just a year later by higher performance tubes which were less likely to encounter this problem, Westinghouse Electric's WD-12 and General Electric's UX-199. No radios using the WD-11 tube were designed after 1924, RCA ceased production and issued a service bulletin describing how to retrofit existing sets to use the newer UX-199 triodes.
Collectiblity
Because of its rarity it has become one of the most valuable vacuum tubes in the world. New-old-stock units have sold for as much as US$180 and used tubes for over $100, more than the original price radios that use them. Collectors rarely, if ever use these tubes for fear of burning them out.
Substitution
Sets that use the costly WD-11 and UX-199 tubes can be modified to use the 1A5/GT octal power pentode (Which cost around $2.50) by wiring a 5.1 ohm resistor between the pins of the filament and fabricating an octal-to-four pin adaptor. The pin for the 1A5's suppressor is left unconnected and the screen connected to the plate.
The type 12 (also known as RCA-12) is electrically identical to the type 11, but with a more common UX4 base.