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

@mulveling 

Thanks for the information.  I checked-out the the MaxiPreamp II & MaxiMatcher that you own.  The metrics seem just what I am looking for, and the pair seem very appropriate who has as many tubes running has your system requires.

Today the price-point (~$2k) seems a bit high for my TWO -12AX7 PhonoPre and ONE 6550-PreAmp.  Still, I have back-up tubes that need to be tested, so I may pull the trigger at some point.

Very best,

 

@mulveling @jea48 @faustuss - thanks for keeping it lively!

... you have made this conversation one of the most strings that I have read on AG in sometime :-)

 

faustuss Regarding the statement "your 6SE it is employed employed as a voltage regulator...", does this imply that the Ref-6 SE's 6550 will likely LAST LONGER (more slowly degrade) than a a similar tubes that are used for direct power output?

Background info: even though the Ref-6 SE's 6550 (Sovteck) is not a power tube, it reaches 180+F, thus it seems to be very inefficient (causing it to degrade?).  Consequently, would you recommend that this voltage-regulator 6550 be occasionally tested like 6550s which are used as power tubes? 

Best

@faustuss 

My friend with the Rogue amp was not tube rolling... the amp was new with less than 75 hours on it using the tubes that came with it. 

@inagroove 

thanks for keeping it lively!

... you have made this conversation one of the most strings that I have read on AG in sometime :-)

 

"faustuss Regarding the statement "your 6SE it is employed employed as a voltage regulator...", does this imply that the Ref-6 SE's 6550 will likely LAST LONGER (more slowly degrade) than a a similar tubes that are used for direct power output?

Background info: even though the Ref-6 SE's 6550 (Sovteck) is not a power tube, it reaches 180+F, thus it seems to be very inefficient (causing it to degrade?).  Consequently, would you recommend that this voltage-regulator 6550 be occasionally tested like 6550s which are used as power tubes?"

Thanks for paying everyone in attendance a massive compliment! This is what these exchanges are all about. I hope we can learn from each other and enhance our enjoyment of the hobby.

Regard the use of a 6550as a voltage regulator, AR's application is unique to me but you should also observe that this manufacturer uses the highest quality circuit components, they're mostly hand assembled along with being rigorously tested and voiced before leaving the factory. AR's reputation as a whole is enviable and has been so for decades.

It is assumed that vacuum tubes are a consumable like motor oil in a car which just isn't the case. Like I mentioned to @mulveling tube electronics have over a hundred years of history and why so many "vintage" products whose manufactures went out of business in the late sixties, early seventies and the equipment is still functional of course with a little rehab and are revered for their sound quality. Likely your AR will function perfectly for decades with nothing more than periodic cleanings and minor recalibration as a matter of course.