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Power Tube Failure

A little while ago a small tube (in my Phono-Preamp) died.  It was a subtle affair in which the tube turned white and the glass cracked, not necessarily in that order.  This failure was interesting, but not dangerous.

Yet, this event got me wondering - what happens when a power tube dies?

My Preamp's power tube runs quite hot, and I am concerned it may be a FIRE HAZARD when that tube fails. 

My second concern is that my Preamp may be DAMAGED when the power tube dies.

So, I am hoping to hear from anyone who has EXPERIENCED a power tube failure and can provide any insight regarding what to expect. 

 

notes:

a. Yes, my Preamp counts hours, but I own several power tubes and do not know how many hours of service each has provided. 

b. Testing these tubes is not plausible - I do not have a tube-tester, and there are no HiFi retailers within a reasonable driving distance.

Thanks in advance for your stories!

Best,

inagroove
katzenjammer27's avatar
katzenjammer27
136 posts
 

may be too late here, but check your voltage. could be spiking at certain times each day.

inagroove OP
262 posts
 

@elliottbnewcombjr 

Thanks, that makes sense as a place to begin.  Yet I need to admit, with Bad (red);  Good (green) my 'Geeky' side dies just a little bit ;-).

That said, I will try to get an instruction manual with whatever tester I purchase.

Best

rettrussell's avatar
rettrussell
237 posts
 

Since '81 I've had a few tubes go out on my entry level CJ amp & preamp.

Usually a fuse blows at the same time, with no fireworks, but I've also had a sparkler show at least once. Loud "blam" occasionally.

My K-horns are so revealing that I replace tubes when the wind noise "whoosh" gets too noticeable.

Guitar amps have been tube-driven from the beginning, so an amp shop is a great resource to test tubes.

Good luck!

 

brownred6
21 posts
 

About the tube testers out there for sale. If the tester measures mutual conductance it is a better one and provides a lot of useful data. If it is not a mutual conductance tester it’ll usually only tell you good, bad , shorted ,not shorted. Mutual conductance testers give you a couple of readings in the chart for new values and minimum values. So you’ll know how close to new it’s available electron supply is , how new it’s performing . 

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