[Amps] Indirectly heated cathodes

[Roger D Johnson]

One of the big disadvantages of the indirectly heated cathode is it's
warm-up time. has anyone experimented with using a lower "keep
alive" voltage to allow faster warm-up when full voltage is applied?
I remember the old TV sets where a diode was in series with the
filament supply and was shorted out when the set was turned on.
Is there an easy way to determine when the cathode is up to temp?

73, Roger

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