Sensibly equivalent¶ to:
215SG CV1018 CV3835 CV3837 KTZ21 VR18
The Z21 is a straight HF pentode and equivalent to the KTZ21 as they are different designations for the same design. The makers data state that it is particularly useful as a sensitive detector.
The Z21 was issued with B4 or B7 base caps.
The reverse carries the Marconi name and on the left is the wire and fixing to connect the metallising to the base.
The classic envelope is 41 mm in diameter, and excluding the B4 base pins is 103 mm tall.
References: Data-sheet, 1040 & 1043. Type Z21 was first introduced in 1937.
Absolute Maximum Operating Conditions¶
Updated March 19, 2014. shape:classic construction:pinch type:pentode age:1930.1940 base:b4 heater:2.0v pins:4 pin:1.g2 pin:2.g1 pin:3.f pin:4.f pin:tc.a