Did it Blow??

tekbow

No, it didn't. Kind of an info post for anyone not familiar with the behaviour of some NOS ECC83's. They do this sometimes, your NOS tube is unharmed. Its called the Mullard Flash, but it's not just Mullards that do it.

I went thru and picked out all my flashers for a full set light show

https://youtu.be/_PEEyqv8hF0

fftc

Cool effect but surely it can't be a good thing?
What is actually happening?

tekbow

@fftc

Low resistance filament wire on a cold start. If i was to turn the amp off and on again straight away you'd not see it happen.

It's honestly not detrimental, and not an indicator of short tube life or anything. Some NOS ECC83's (82's, 81's and probably other euro made preamp tubes also) do it, some don't.

Maynehead

My Brimar does this too, I think it's pretty cool. I'm guessing it's a heat related phenomenon where the filament has more resistance when cold or something along those lines...

tekbow

@Maynehead

Nearly exactly that, yep. or could be exactly, it's something along those lines. One of those is a Brimar, nice tubes.