I think I see where Stevecham is going with his question - Amperex (Holland) small signal tubes will 'flash' when first powered up, and it's totally normal with those tubes.
On the other hand, I've had power output tubes 'flash' on me, blow a fuse, and test fine afterwards (all EL34's for what it's worth) but I've learned to think of my tube tester as a rough way to weed out obviously failed tubes, not a final arbiter of good tube vs. bad tube. A lot of my tubes have tested well, but were noisy/fuzzy or microphonic or had less output than a tube used in the opposite channel that tested exactly the same.
Have you seen those old Upscale Audio ads that say "we don't use your amp as a tube tester!"? Don't use yours as one! If an output tube flashed, don't risk putting it back in your amp, regardless of what your tester is telling you.
Just my opinion, of course. Good luck!
