If a picture tube loses its vacuum...

[andy]

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[ChrisW6ATV]

Originally Posted by andy

Are you sure that was a tension band and not just a mounting band? I cut the tension band on a CRT once (after it was up to air) and it was under such tension that it broke very violently.

Yes, I would call the band on these CRTs a mounting band, not a tension band. I wonder if the mounting band "protects" anything once it is installed?

[compucat]

If a picture tube loses vacuum in an empty cabinet, does anyone hear it hiss?

The biggest problem with rebuilding CRTs that have gone to air is that the phosphor degrades.

[compucat]

If a picture tube loses vacuum in an empty cabinet, does anyone hear it hiss?

The biggest problem with rebuilding CRTs that have gone to air is that the phosphor degrades.

[kx250rider]

Originally Posted by compucat

If a picture tube loses vacuum in an empty cabinet, does anyone hear it hiss?

The biggest problem with rebuilding CRTs that have gone to air is that the phosphor degrades.

It depends on what happens to the tube. If it develops a slow leak at a glass-to-metal seal (as with 15GP22 and 21AXP22 often,) you'll never know it. It can take years and years. I had one 15GP22 that was starting to lose vacuum, as evidenced by bright blue glow in the neck. Later the filament got brighter and brighter, then after about 2 years, it started arcing when enough vacuum had been lost.

In cases where the tube gets busted, either by a high voltage regulation problem (many Zeniths in the 70s, and in many newer projection sets,) you hear "Krack- HISSSSSSSSSsssssssssssssssss". If you snap the neck off, you hear "KSHTHWUPF" (Try to pronounce that )

Charles

[peverett]

I have opened boxes with NOS receiving tubes that had gone to air without ever being used. Probably a manufacturing defect that caused a small crack in the glass.