Bad tubes or good tubes 415's

[MesieBooga]

Hi guys! I have a bunch of Mesa 415's that I picked up here 'n there. How do I know what is good to use and whats not?
What is a reliable tube tester to pick up?

 

[Platypus]

willing to share the wealth?

 

[MesieBooga]

I would but I like them and as you know they are hard to find. Plus I don't know whats good and whats bad. Hence this thread... :lol: I might have blown some this morning. That or some expensive 450's.