WD-11

From Wikipedia, the free encyclopedia

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 WD11 and "RCA-11"[1] (and later simply named "11" by RCA[2] and Philips/Miniwatt[3]) have the following characteristics:

Socket: UV4 (also known as WD-4-Pin)
EIA/RETMA Base Diagram: 4F
Description: Detector Amplifier Triode
Filament: Directly heated 1.1 V 0.25 A
Plate (anode) Voltage: 90V 135V maximum
Grid Voltage: -4.5V -10.5V
Plate Current 2.5 mA 3.0 mA
Plate Resistance: 15.5 kilohms 15 kilohms
Amplification Factor (mu): 6.6 6.6
Transconductance (gm or S): 0.425 mA/V 0.44 mA/V
Power Output: (Po): 0.007 W 0.04 W[4]
Grid-plate Capacitance (Cga): 3.3 pF
  1. ^ RCA Receiving Tube Manual RC-13. 1937. p. 98.
  2. ^ RCA Receiving Tube Manual RC-14. 1940. p. 157.
  3. ^ "Miniwatt" Technical Data (6th ed.). Australia: The "Miniwatt" Electronics Division of Philips Electrical Industries Pty. Limited, N.S.W. 1958. p. 56.
  4. ^ "WD 11". Retrieved 7 January 2013.

Drawbacks[]

Westinghouse WD-12
RCA UX-199

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 and subsequently burning out the filaments on the remaining tubes,. The WD-11 also has a unique 4 pin base layout that was unlike any subsequent UV and UX style tube base. It had 3 "small" pins and one "large" pin. (Later UV based tubes relied on an index pin on the side of the tube base and UX tubes had 2 large and 2 small pins to ensure proper indexing.) 

 It was replaced just a year later by higher performance tubes which were less likely to encounter the filament shorting 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 of the 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 UV-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.

External links[]

Here is a link on how to modify other tubes to use in place of a wd11:

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