THE LIFE OF A VALVE
With careful use a valve should retain its full efficiency for 2000 hours. The chief cause of degeneration is too much current in the filament. Valves should not run any brighter than is necessary to give satisfactory results. A high plate voltage may also result in deterioration if a C battery giving grid bias is not used; Most valves that have lost their sensitiveness can bo re-activated to some extent. Try leaving them lit rather brightly for two hours with plate battery disconnected. Then test the emission by connecting the B battery with a milliameter in circuit. If this is not effective more drastic treatment is justifiable. The process of “flashing” may be tried. This means applying a filament voltage of twelve volts for dry battery tubes or eighteen volts for tubes of the 201 A type for fifteen to twenty seconds with plate battery disconnected, and then repeating the two-hour treatment first suggested.
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Manawatu Times, Volume XLIX, Issue 3491, 29 October 1926, Page 4
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159THE LIFE OF A VALVE Manawatu Times, Volume XLIX, Issue 3491, 29 October 1926, Page 4
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