WD-11
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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. 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 theWd-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. Because of its relative paucity it has become one of the most valuable vacuum tubes in the world. At the time of this writing, new-old-stock units sell for as much as $180 and used tubes can sell for over $100, more than the radios that use them. Collectors rarely, if ever use these tubes for fear of burning them out. Sets that use the costly WD-11 and UX-199 tubes can be made 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 supressor is left unconnected and the screen is to be connected to the plate.
