Recycling tubes

[Tony Allgood]

Hi folks,

A little while ago I asked the list about information about valve
amplifiers. I am thinking of doing a valve project, perhaps a pre-amp. If I
have some old valve amps, can I use the tubes inside? I know they don't last
forever, how can I test if they are alright? I read somewhere that hum will
increase as a valve amp gets older, is this true?

Tony Allgood

Cumbria, UK