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3A/172BSensibly equivalent¶ to:
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The 3A/172B is an indirectly heated triode. The prototype was the 4D1. The old GPO code is POVT100B as it was used for telephone repeaters.The KB/F identifies this valve as being made to specification K1001 or K1006, the B denotes qualification by a UK authority and the F identifies the maker as STC, Paignton.
The triode assembly.The classic envelope is 38 mm in diameter and, excluding the B7 base pins, is 95 mm tall.Reference: Data-sheet. Type 3A/172B was first introduced in 1950. See also 1950 adverts. |
Pin Connections
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | tc |  m | nc | nc | h | h | k | a | g1 |
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Absolute Maximum Operating Conditions¶
| Vh | Ah | Va | ra | gm | μ | 
| 13.0 | 0.2 | 250 | 10,000 | 4.0 | 40.0 |
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Updated July 23, 2025.
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