Hi Guys,
Just wondering...
Image Link

The pic is upside down, the base is at the top of this pic, but there are no pins near that mark, or any visible cracks in the glass.
There is a small element looking part directly behind that mark. Could it be anything other than gas making that stain?
Cheers, Art.

Looks like the getter to me, which is a pocket of inert gas that is deliberately leaked after the valve is sealed to stop any leftover oxygen burning the filament out.

Well that would be good news thanks

Sometimes the getter appears as a chrome 'cap' inside many valves though in others it is just grey muck. It depends on the valve.

I only knew about the chrome cap. You learn something new not every day, but a lot of days
That's more good news, this one doesn't have one.

That's a dead valve!

The mark on the valve is what remains of the getter flashing. It should be silver/grey in colour and look like chrome. When it reacts with air it turns white and powdery looking which is what has happened with the valve in your photo.
The valve doesn't need to be cracked to leak, a failed seal on a valve pin will allow air to leak in over a period of years.

That's not so good news!! Edit, all is not lost, I do have a source for one..

TV collector is right, the vacuum has leaked out.

That's probably going to be a good thing because it's a transmitter final, and probably why the unit is discarded.
Since the receiver is fine I don't anticipate a whole lot of other problems.

Lets hope a valve is available - they don't look like a common variety...

It's definitely all good I got a guy I'm keeping secret

I have a collection of valves that have been dumped here & need sorting and I am quite sure that I have seen QQ numbers. Which particular lot ...... that is the question.

Marc

I have a fairly good collection, but most are TV valves and not so relevant to my interests, but I have saved some test equipment out of it without having to go buy valves, so decided never to chuck anything.

There is a fellow with 8/2 of these in stock NOS/used (or vice versa) ,who will charge me 5-10 dollars.
The reason I don't think it's a good idea to spill it in public is because there is huge potential for someone to make money out of him on eBay, and deplete my supply in doing so! At the same time, I'm keeping an eye out for threads requesting specific types.