Valve Gallery - Screened Tetrodes And Pentodes (3)

Valves: DF1, EF9, KTW63, KTZ63.

Shown above is a Mullard DF1 valve.  This rather less common valve was designed for a battery receiver, probably portable.  It features a heater of only 1.4 volts, with P Type CT8 base. Height of 93mm. Shown above is a rather dirty Mullard EF9 with P Type (CT8 base).  This is a var valve with 6.3v heater.

Shown above is a Marconi Osram KTW63. This is the var u version of the KTZ63 next picture. Otherwise similar characteristics, though slightly shorter envelope at 117mm.. Following from previous caption, above is the KTZ63 then.  Heater voltage is 6.3v, International Octal (I.O.) base, but a little taller at 122mm.

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