Quote:
Originally Posted by Boater Sam
I am continually amazed that the CRTs still hold a working vacuum after 70+ years, does not helium infiltration destroy them at least in part?
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I think you may well be right about this.
I have found that the worst affected CRT's are the relatively thin walled pyrex ones. The most notorious for this are the pre-war 5BP4 and 5AP4, new old stock, often rendered useless. The VCR97 has a thicker wall than the 5AP4 and 5BP4 and these are a little better, on the average. However, the thicker walled (basically soda glass) CRT's of the post war period, especially NOS ones, seem to do much better with respect to gas infiltration. Used ones can suffer from aging with loss in cathode emission & phosphor degradation & ion burns, but new ones are usually just fine.