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The 12BY7 is a miniature 6.5 W power pentode tube. The 12BY7A (European equivalent EL180) is a compatible and slightly improved version.

Both are all-glass types with a B9A (Noval) miniature 9-pin base and share the EIA 9BF pinout with a number of other miniature pentode tubes of the era.

Tek part number: 154-0047-00 (12BY7A)

Aged/Checked/Matched Pair Details
Used in Tek Part# S/N Range
531, 533, 535, 536, 541, 543, 545, 555 157-0053-00 ?
106 157-0115-00 Note 1

Note 1: Made obsolete soon after the number was allocated.


Tube aging procedure / Selection and checking procedure

Data sheets and Links

9BF socket diagram

Used in

  • the output stage of the 1121
  • the first stage of the 535, 545A, and 555