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In Reply to: RE: Reflashing Tubes? posted by Lee of Omaha on November 02, 2014 at 12:01:11
Eli's.correct. The getter flash material once initially flashed cannot be reflashed.
However i have had great success with baking out gassy tubes to activate the getter flash without voltage being applied.
I believe getters get heated in operation, and are supposed to absorb stray gases, the voltage maybe ionizing them. Heating externally will activate getter flash and do a better job in my experience.
I use a toaster oven set at minimum and raise temp 50 degrees F every 30 minutes to 300 degrees and hold for several hours. When done I unplug toaster and allow to drop to room.temperature.
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I think what he's asking is can the getter be re-flashed when it wasn't flashed completely at the factory. I've seen this before, in fact I have an old stock Sylvania 6L6 that didn't spend enough time in the inductive heater, and as a result, the getter material is still in the halos, and not on the glass.
I actually sent an email to Ron "Glasslinger" on Youtube, the guy who makes tubes, and asked him about it. His advice was don't bother, American tubes were vacuumed down VERY hard, and the getter was more of a belt and suspenders, and not really needed to keep the tube from being gassy.
I'd still like to flash that tube, though it would be cool to watch, plus it would match the other three much better!
Does anyone have any advice or plans on making an appropriate induction heater?
I've seen a video of a tube's getter being flashed. It takes about 2 seconds.
My understanding is that the getter material works by adsorbing gas, that is, the surface of the material does the work. So if there's getter material in the halo/d/disc/whatever reflashing it will deposit more on the glass where it can adsorb (no absorb) gas.
Baking is another option.
Morgan Jones recommends warming NOS tubes in the oven for a few hours before using them to tidy up the vacuum and avoid problems. Same idea I think.
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