2. amps-preamps
  3. 185575-111109

Is this describing a blown tube, or two blow tubes?

I installed a new set of JJ e34’s a few days ago. Last night there was a very loud POP and one of the tube went bright so I moved quickly and turned of the midmonos.

 

After they cooled I inspected the tubes and they seemed fine so I reinstalled them thinking maybe it was some kind of impurity within the tube. I’ve never experienced a blown tube before.

 

The amps ran great this evening until just now, and another POP and bright tube, but it seemed like it was the other tube, but I can’t be sure. This was followed by a low whistle or hum and I turned the amps off again.

 

Is this simply a run of the mill faulty tube? Could two blow in one day, or could the first one POP like that and then continue to work for another day?

 

Since Ive never experienced a tube fail before, could this have anything to do with the Amp, or is it just a bad tube or tubes?

 

Should I worry about putting my old tube back in?

 

Thank you,

 

TD

 

128x128tonydennison
jayctoy's avatar
jayctoy
3,732 posts
 

Op it happens to my preamp JJ Tube does that.And I never reinsert that tube again.

tonydennison's avatar
tonydennison OP
382 posts
 

@glennewdick 

"could also be small particles left over"

 

That is what I thought at first since the tube still worked. The second time there was a whistle, so certainly different.

I emailed mike sanders last night and he said it sounded like a normal tube failure and that a failed tube can work for another day until the failure is complete.

 

T

tonydennison's avatar
tonydennison OP
382 posts
 

@jayctoy 

"And I never reinsert that tube again."

Yeah, I just figured it was a particle.

:-)

 

jea48
4,307 posts
 

@tonydennison 

Before installing new power power the bias pot(s) should be turned back (turn the bias pot(s) counterclockwise), so as to not over bias the new tubes. Not doing so can damage perfectly good new tubes.

"Output tube bias should be set immediately when new tubes are put in; then again in 15 minutes;"

Did you do this before and after installing the new tubes?

 

You said you reinstalled the old tubes and the amp works fine. Just a guess the bias setting was still set for the old used tubes. Is that correct?

tonydennison's avatar
tonydennison OP
382 posts
 

@jea48 

"

"Output tube bias should be set immediately when new tubes are put in; then again in 15 minutes; Did you do this before and after installing the new tubes?"

I did both of those things, yes, and Ive checked the old tubes' bias  I just put back  a few times and they have settled.

 

Thanks for pointing this out, just in case.

 

TD

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