Is this a dying tube?

tschelle668

Silver Supporting Member
Messages
483
This amp started hissing and popping a couple of days ago. I was checking all the connections and when I noticed the smell of burning hair, and I searched the forums and found lots of talk about how awesome hot tubes smell. This is not a good smell. And it's not a new tube so it's not paint burning off. I didn't pull the back panel off, because I don't have any replacement tubes yet, but I did order some. Is this most likely a bad tube, or something more serious???





 

recto-robbie

Member
Messages
2,322
Yea I wouldn't keep doing that, it looks like that tube is about to melt. Replace the tubes and when you turn it on for the first time after replacement watch the power tubes to make sure they don't start glowing red hot like that again. Hopefully all is well after the replacement. Good luck.
 

UncleLarry

Member
Messages
2,246
That tube is redplating. Something is seriously wrong. Don't continue using the amp in this condition. It could be the tube, the amp bias, or a leaky cap could be causing oscillation. Try changing the tubes out with a matched pair. If you get the same problem, take it to a tech.
 

Dan40

Silver Supporting Member
Messages
2,096
Agree with UncleLarry, your tube is either shorted and drawing excessive current or you may have lost bias voltage. What amp is this and do you know if it is fixed bias cathode biased? Either way, do not run the amp again in this condition or you may damage other components.
 

CallEOD

Member
Messages
2,104
You have a runaway bias on one power tube.
Bad bias supply filter cap or maybe a burnt SGR ?

Need a re-tube and a shop visit.

Not a huge deal but it can get much worse if you don't fix it.
 

Blue Strat

Member
Messages
30,722
For a little clarity, you could try swapping sockets with those power tubes. If the same tube continues to redplate the tube is the problem. If the other tube in the same socket redplates, then it's the socket or circuitry associated with the socket.
 




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