HOW DO TUBES NORMALLY GO?

[oldgeezer]

Most tubes slowly lose output at end of life. However, they maintain close to full output during their entire life. They drop off quickly like off a cliff.

 

[Danzik]

What type of heat is needed to actually soften glass?
I'm assuming it's enough to quickly fry a steak.
Or Worse, have someone looking like Fire Marshall Bill. (Or was it Bob?)

It was Bill. " LET ME SHOW YOU SOMTHIN" ! LOL

 

[nomadradio]

Used to have a couple of 6JS6 or 6JE6 tubes that had softened the glass on opposite sides where the anode got hottest. One of them was just sucked inwards, a crater on each side. The other one sagged enough to touch the anode and opened a small hole at the pit of the crater. The tech I employed at the time made a poster out of cardboard with this tube strapped to it, and advice on how not to be "this guy". Lord knows where that went.

73

 

[Onelasttime]

Normaly it is slowly over time even when driven hard but not abused it is slow. The other way is something else besides the tube lets go inside and you get massive arcing and not only is the tube gone and your underware but a lot of other parts are gone as well. This is rather rare though. I have never seen it happen myself but have heard of it happening.

It is kind of strange because tubes kind of remind you of a mechanical device like an engine that just slowly wears out and you do not even notice it until you reach a threshold. Suddenly it seems like the engine slugish. Sure some guys put a window in their block but that is not typicaly how an engine wears out or fails!

In the old days if the power output was down but no shorts or gas leaks you would pull the tube, put in a new one, check the old one, toss it in the box for the new one and write old, used, good and write the numbers on the box or the tube just in case the new tube failed suddenly!