Quote:
Originally Posted by Kevin Kuehn
Maybe as long as there's no beam current, the cathodes not taking a beating, and leaving the filament lit may actually save it from premature burn out?
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Not sure about that. Operating tubes for long periods of time under cutoff conditions contributes to a particular form of degradation called "cathode interface formation" (aka "Sleeping Sickness"), in which the active emitting oxides interact with the cathode base metal to form a resistive layer which in turn begins to "insulate" the remaining active oxides from the base metal. This caused all kinds of problems in vacuum tube computers, which might have flip-flops and gates that stay cutoff for hours at a time. Eventually, special cathode chemistry (ultra high purity nickel alloys) developed for computer service to combat the problem, but ordinary TV types (including CRTs) aren't likely to use them.
Probably the reason that sets with "instant-on" almost always have dead CRTs....
11-26-2013, 01:01 PM
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