Why does this keep happening to my PI tube? Pic included.

[dB]

First a Mullard and now a Telefunken. What's causing this to happen?

Both times the glass cracked at the base and the top got completely smoked. The only thing that I have been doing out of the norm is not using the spring loaded tube cover that holds it securely in place. Not sure how that would cause this to happen, however.

 

[VacuumVoodoo]

Skewed pins can do this.

 

[mbratch]

Yeah, the white means that there's air getting in, but that's probably obvious from that huge crack. When does the crack occur? While you're putting it in? After you've played it a long time? Got a pic of what it looks like when mounted in the amp?

 

[ski_fast]

You should buy a tube pin straightener. The "star" ones are only 5-10 bucks and they will have ten holes. A lot of the Mullards and Telefunkens are used, which is okay, but many times when being removed the pins get bent. When the glass gets hot you may be getting just enough expansion at the stress point of a bent pin to ruin the tube. Just my guess...

 

[SatelliteAmps]

What kind of amp is it? Some amps with circuit board mounted tube sockets do not have enough space on the chassis for some tubes to fit. This can lead to cracked tubes (even if they do fit, sometimes just having the hot tube touching the cold metal of the chassis is enough to crack them).

 

[donnyjaguar]

I hate when this happens. Agreed with the others except I'd replace the socket with something new. This problem is unique to non-octal types.

 

[RussB]

Check the voltages, maybe some component is amiss and the tube is running too hot