The 30C17 is a triode variable-mu pentode designed for television frequency changer use. When introduced it was the first variable μ TV frequency changer to be available in the UK.
The frame-grid variable-mu pentode enables the AGC line to be applied to the mixer and avoid overloading on strong local signals. The intended frequency range was VHF.
The perforated cylindrical screen encloses the pentode but not the triode.
Both cathodes are connected together internally. The triode grid supports are strapped together top and bottom and thus make the frame of a frame grid.
The thin glass tube envelope is 20 mm in diameter and, excluding the B9A base pins, is 46 mm tall.
References: Data-sheet, Data & 1040. Type 30C17 was first introduced in 1961. See also1961 adverts.
