Quote:
Originally Posted by Zenith6S321
I found this article/advert:
http://www.saesgetters.com/sites/def...Features_0.pdf
that says once the getter is heated to 800 deg. C there is a chemical reaction that raises the getter to 1250 deg. C and this event is visible by the quick change in color and brightness. Did you see this when you flashed the getters?
They do say that using too much power will also result in not enough barium deposited. Sounds like all of this is a real art. |
About all I saw was the getter ring ramp up slowly to a red then orange then yellow heat, and a few white "sparkles/flashes" on the surface, which was presumably remnants of the active material. Intentionally overheated a couple to the point where the getter ring itself melted, and no difference.
There is a lot of interesting technical discussion of getters in RCA's 1962 "Electron Tube Design" manual, which is available online in a few places. Apparently, some types do only yield about 50% of the free barium on initial firing, but once the tube goes gassy, presumably the bulk material left in the getter cup starts oxidizing, as well. Getters are packaged under vacuum, and stored in an inert atmosphere before installation into the tube. Sitting for decades in a gassy tube can't do them much good, even in an unfired state.