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[Bottom line: A CRT new in the box, with excellent vacuum, should stay as new forever. But one with poor seals (15GP22, and any metal/glass combination), or any CRT with less than excellent vacuum (Sony from the 80s/90s, Mitsubishi projection from 90s, etc) will deteriorate no matter what, but can be kept alive longer if the filaments are warm all the time.
Charles[/QUOTE]
You are SO right on the Mitsubishi CRT's in their Big Screens. I worked on one today, a 97 model or such,and the tubes are Shit. I mean, they work, but they have that "soft" look, that mits tubes are known for. whereas, my '94 RCA BS with hitachi tubes looks better than some new sets. I am sure that probably 85-90% of the tubes life is still there. This is NOT the exception, rahter the rule, where those RCA sets (and hitachis too) from the late '80's to late '90's are concerned. The tubes seem to be nearly bulletproof, and last and last and last. I have seen only a handful of bad ones, out of many hundreds of them I have worked on, compared to many bad mits. tubes. To me that is SAD, because Mits. was SUPPOSED to be superior to Thomson(RCA) but the tubes (and caps on the boards) sure arent!
I figure, that the Hitachi tubes must have well evaporated cathodes with a lot of VERY pure material, and a very good vacuum, whereas the MIts. tubes probably have a softer vacuum, with less material evaporated on it, and less pue too. (RCA direct-view tubes from the last 20 years or so are similar in this regard,of very high quality and durability, only recently have they switched to a "crappy" tube, to cut cost.)
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