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Doubts on cathode stripping in tubes
Doubts on cathode stripping in tubes
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Old 19th January 2016, 03:43 AM   #41
wrenchone is offline wrenchone  United States
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Indirectly, this the rationale for using hydrogen/deuterium as fill gas in HV, high power thyratrons. The lower mass/charge ion has less of a tendency to blow hell out of the large area, high emissivity cathode surfaces needed for a good high power thyratron. Xenon, neon, and mercury fills are used for lower operating voltages.
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Old 19th January 2016, 05:31 AM   #42
cerrem is offline cerrem  United States
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There are cases of cathode stripping during start-up of receiving tubes where the Heaters are "floating" on a DC voltage derived from the B+...
The damage occurs due to the Heater to Cathode voltage is greatly exceed for a short time before the B+ pulls down to it's loaded state.... Very repeatable....you can hear the clicking sound of the arc..
Simple fix is to put a protection zener on the voltage divider ...this way the zener clamps only during start-up, preventing an over-voltage on the Heater...
Problem 100% solved ...

Last edited by cerrem; 19th January 2016 at 05:34 AM.
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Old 19th January 2016, 07:47 AM   #43
Guido Tent is offline Guido Tent  Netherlands
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Quote:
Originally Posted by Bandersnatch View Post
If that were the case, no IDH rectifier would survive turn-on.
cheers,
Douglas
of course I am talking long term use, incidental cases do not harm
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Old 8th April 2016, 07:02 PM   #44
Uunderhill is offline Uunderhill  Canada
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To point out, here is an article called Kindness to Filaments by John Harper.
http://www.john-a-harper.com/FilamentHeating/index.html
To be kind to the heaters, he suggests doubling the heater supply voltage,
but a resistor is connected in series with the heaters.
The value of the series resistor is the same as a warmer up heater.
.

Last edited by Uunderhill; 8th April 2016 at 07:28 PM. Reason: technical correction
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Old 9th April 2016, 09:24 AM   #45
DF96 is offline DF96  England
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Normal AC heater supply is sufficiently kind for most purposes, as the transformer resistance limits surge current.
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