[Ron Ramirez]

I have had good luck with super glue on grid caps, but it will cause the glass to crack at the base if used on the base of an audio output or rectifier tube...any tube that runs very hot.

If a tube base were to come completely off, I think I would try some Sauereisen cement. It is used to hold burner collars and fill cap collars on glass Aladdin lamps. Now there is a good example of unequal/uneven heating. The upper parts of the burners (chiefly where the flame is) reach 1000+ degrees while the glass font remains basically cool.