Hi Charles:
I read through a two decades old PHd thesis on CRT cathodes. ( as anyone can too! There are any number of people posting here who will first humiliate one.. but, explain things one might not understand.)
I also read through the "B&K 467 Cathode Ray Tube Restorer Analyser" manual. (There's even a nifty picture of Karl Corn inside the front cover... yes, those were the days!)
In my opinion, people working with CRTs in the field (TV repairmen, video game repairmen) contributed to forming a model that was sufficient to explain a methodology... so that engineers (at B&K, Sencore and others) could design and build things like the 467. But to my knowledge the "model" that was used, by those designers, was never sufficiently explained scientifically. And the thesis referred to above offers several competing models: about what happens as CRT cathodes/filaments age, degrade, or become poisoned.
Just the same, I've seen several topics and posts ..,here on TekScopes ... about, "welding filaments", rejuvenating/brightening/rebuilding, old oscilloscope CRTs.
As far as I cant tell, a lot of what is reported on the Internet, about "rejuvenating" CRTs ... regarding "how rejuvenation works" and "whether it works" is foolishness.
Yes! TV repairmen did "rejuvenate/brighten" TV CRTs (using self devised methods, or gear like the 467); but, the old-timers that I knew ... they related that it was a temporary strategy. It allowed them to "rejuvenate" the CRT, on site, while they ordered in a new (or rebuilt) CRT. Rejuvenation didn't last very long!
There might be something different about the CRTs Tektronix used (and made) that might allow "rejuvenation."
But bear in mind that as far as I can tell, no CRT was designed to reliably withstand the peak pulse power (or the relatively large average current/voltages) that rejuvenation gear (or home-brew hacks) apply between the cathode and grid (or to the filament).
Best regards.
--
Roy Thistle
