Re: {Collins} Eimac 3-500Z tube value?

The 3-500Z won't "re-getter" from just the filament being applied.  You have to apply high voltage and get the plates showing red to have any chance on reviving the tube.

Now ceramic tubes (i.e. 4CX250B) can usually be revived by applying heater ("filament") voltage for a period of between 24 and 48 hours.  Unfortunately, this doesn't usually work for glass tube like the 3-500A.

Glen, K9STH


--- On Sat, 6/27/09, Jim Monk <jmonk1@xxxxxxxxxxxx> wrote:

Concerning the problem of Oxygen Migration in PA tubes such as the 3-500Z as being currently discussed on this list....... has anyone had experience in "re-establishing the getter" by energizing the filaments over an extended period of time and then later "ramping up" the HV to the plate utilizing a variac or similar device.
This procedure is reported to help avoid the "flashover" which can occur when the tube has "been on the shelf" for long periods of time and then energized with the normal HV, causing tube failure.
It is my understanding the initial vacuum as established in manufacture is frequently lost when the tube has been stored and unused for long periods.
I have two Military 3-500Z tubes still sealed in the original boxes and plastic packaging and would appreciate any thoughts on the effectiveness of the above procedure to avoid failure of the tubes, if and when I need to install one of them.


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