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The type Z66 was M-OV's late-1930s in-house attempt to make a small, modern high-slope pentode for wide-bandwidth IF systems in TV and radar, where bandwidths of several MHz were required. Production seems to have been post-war.

To ensure that the valve would be cheap and easy to make, a 'pinch' construction was used that could be assembled on existing production line machinery. Sadly the Z66 was very much a 'second best when it came to performance, particularly in terms of gain-bandwidth product and high-frequency noise figure.

The high bandwidth receiving valve that won the War was the pinch-less EF50 not the Z66, even though they had comparable data-book characteristics. The extra lead length added too much inductance.

The silvering on the inside of the glass obscures some features but at the correct angle the grids can be seen. It is a true pentode with a wire g3. The latter is the most easily seen feature in the picture. All three grids are wound on notched and peened rods and there does not appear to be much tension used in the winding process.

The wide glass tube envelope is 28 mm in diameter and, excluding the IO base pins, is 81 mm tall.

Reference: ¹⁰⁴³. Type Z66 was first introduced in 1948. See also 1948 adverts.

Pin Connections

Absolute Maximum Operating Conditions^¶