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#1
09-29-2007, 01:23 PM
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It seems that when the vacuum has failed, and the tube sits neck-up for many years, the phosphor gets dark angular blotches. Now even the one in a CT-100 that I have is doing that, and I was told that the CRT in that one was confirmed non-vacuum as of 1980. That set spent 15+ years in a garage, but has spent the past 15 years since then in an indoor climate. So maybe the phosphor starts taking on humidity or something after a period of time, more so when the tube is on it's face?
Charles
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Collecting & restoring TVs in Los Angeles since age 10 
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#2
09-29-2007, 05:04 PM
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Blackheads...?
Inspected two 15GP22 duds under a strong light and came up with zero blotches... until I used a magnifier and found a sea of mini 'blackheads' that are much tinier than a phosphor dot. Can't say for certain that it isn't contamination during manufacture, but it doesn't quite look like that. The other dud doesn't have the blackheads. However, the thick glass faceplates are full of tiny air bubbles and bits of grit; just focus your magnifier inside the glass to see it. And although I can't quite perfectly focus my magnifier on a good phosphor dot plate (because of the CT-100's safety glass) they do seem to be 'blackheads' free.
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