Disturbing pop/crack

After an evening of enjoying my M125's I had something happen on power down, a very loud pop when I turned the toggle switch off to one of my M125s. It was late at night so I waited till the next day to powered up my system and listened to some music which was clean and enjoyable as ever. When I turned the amp off....POP...

After letting it cool down I did a look see around to find anything obvious to cause the "pop". Everything looked fine, fired it back up without the preamp running and did some voltage checks, all normal. Turned it off again and "pop" kind of loud. What I found out to be the problem was one of my driver tubes, an old 59 RCA clear top 12au7a. It played fine but pops during shutdown.

I had some more of these tubes and replaced it, and everything is good. I'm just curious if anyone has encounter this before?

Terry from Tennessee

tubes wear out. If you consider the heat stress they go through, it is amazing they last as long as they do, especially one dated from '59!
Throw it out, it has had its time!

MontanaWay wrote:tubes wear out. If you consider the heat stress they go through, it is amazing they last as long as they do, especially one dated from '59!
Throw it out, it has had its time!

but but but...I'm a 1953 who pops and cracks, would ya throw me out...

I put another '59 tube in, I have a few more of them.

C'mon, Terry, Rice Crispies snap, crackle and pop. When tubes do this, they're well done. Give the tube a Viking funeral in the bathtub and sail on.

Had a pre-amp tube (6CG7) just this week go south on me; wouldn't even pass a signal, just loud noises.
About my age, mid-60s. Yes, a Viking burial is in order.