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This valve is marked as distributed by Ediswan and carries the Type designation of EF85. The companies own brand - Mazda - made the identical 6F26 it would be interesting to find out why this valve is so labeled.

The EF85 / 6F26 is a VHF varible-mu pentode where the stage gain is controlled by the negative bias applied to the control grid. At the time this design was developed television receivers operated on Band I at about 50 MHz and from 1955 also on Band III at around 175 MHz. The 6F29 frame grid pentode, released in the 1960s, overtook its performance.

When Band IV and Band V UHF television entered service in the early to mid 1960's the front end required specialised triodes to operate at 400 - 850 MHz.

The valve was made in England.

The thin glass tube envelope is 20 mm in diameter and, excluding the B9A base pins, is 58 mm tall.

Reference: Data-sheet. Type EF85 was first introduced in 1951. See also 1951 adverts.

Pin Connections

Absolute Maximum Operating Conditions^¶

Thanks to Frank Philipse for supplying the above PDF datasheet.