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This exhibit looked to be a mystery with no reference to a Type Z8152 in the literature. An internet search found an entry on worthpoint.com showing that the Z8152 was a GEC valve equivalent to the MH4. The style of etching on the glass is certainly to the M-OV style. The presence of a contact wire external to the base shows that a metallic screen was used on this type of valve. So it is possible that the Z8152 is an M-OV internal code and that the finished product would have been a screened MH4. It is also possible that a redesigned MH4 in the shouldered envelope was called a Z8152.The MH4 is an indirectly heated amplifier triode. The MH4 was also produced in Catkin form in 1933/4. The glass envelope version has a totally different electrode construction but gave the same results. The Catkins were excellent valves but were more expensive to make and were phased out after a few years.

The wire used to connect to the metal paint.

The classic envelope is 44 mm in diameter and, excluding the B5 base pins, is 93 mm tall.

References: Data-sheet & Internet. Type Z8152 was first introduced in 1929. See also 1929 adverts.

Pin Connections

Absolute Maximum Operating Conditions^¶

Thanks to Frank Philipse for supplying the above PDF datasheet.