Quote Originally Posted by Mick
Thanks for the replies guys! Extra thanks to oldguy for checkin' out my pics. I'm glad you like 'em.

So, I just tap on the tubes and listen for strange sounds, eh? I guess that sounds easy enough. Even for me.

In fact, I'll go give that a try right now.
A microphonic tube will be obvious, kind'a the dental hygenist hitting the exposed nerve.