>
>Some of the larger tubes list the maximum surge current for filaments at
>switch on. Has anybody any idea what the limit should be for smaller tubes,
>such as 4CX250B, 4CX1000 etc?
>
>I'd guess at twice nominal operating current as a safe figure, but any
>ideas?
>
For indirectly heated cathode tubes, I have seen no mfg. spec. indicating
a need to limit heater inrush current. My guess is that the hot/cold
resistance ratio in heater type cathodes is much less than that in
directly heated/thoriated-tungsten cathode tubes. Typically,
directly-heated cathodes have a hot/cold res. ratio of 8.3 to 1.
- later, Peter.
Rich...
R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
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