[fado]

This is an old GZ34 used in my Modwright LS100. The glass part does not deflect noticeably in the metal base along the vertical axis but does rotate in the metal base slightly ~ <1mm. Is it better to leave it alone and just be very careful with it or is better to try a fix? If so, what are appropriate repair/stabilization approaches?

[JakeJ]

If the glass envelope and its vacuum is intact and there is no gas then I say stick to your title for advice.

That's my .02.

[Ericus Rex]

+1

[JohnR]

Not that I've tried it, but a drop of epxoy may help stabilze it. If it's in an amp, just leave it there.

[JakeJ]

If you do try the glue repair be sure to use one that is high temperature resistant.  Gorilla Glue claims it is but I could not find any numbers to confirm how high.

[fado]

Thank you for the advice so far. My tube knowledge vacuum probably exceeds that of the tubes themselves.
This tube is used in a preamplifier and is functional, but what indicators mark vacuum and gas problems?

[Alberto DeRoma]

If it's working well, I would definitely, 100%, no questions ... leave it alone.

Alberto

[JakeJ]

Thank you for the advice so far. My tube knowledge vacuum probably exceeds that of the tubes themselves.
This tube is used in a preamplifier and is functional, but what indicators mark vacuum and gas problems?

Break down of the vacuum allows gas (air) inside.  The primary visible sign is the flashing (silvery coating inside the glass) turns white.  The best way to find out if it is getting gassy is to test it on tube tester that can test for gas.

Check out this YouTube video
https://www.youtube.com/watch?v=sn2YIynXbzY