The B5 triode is from the mid 1920s and is marked with the BBC stamp. The base is B4 and the filament required 3 Volts. The envelope is opaque an no details are visible above the pinch.The balloon envelope is 35 mm in diameter and, excluding the B4 base pins, is 83 mm tall.Reference: 1003. Type B5 was first introduced in 1923. See also 1923 adverts. |
