Power Tube Failure

@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

errata;   one of the most INTERESTING strings...

@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.

@mulveling 

" E88CC (6922 / 6DJ8), not E83CC. 12V is definitely no-bueno on the former. I goofed because I have a preamp with an internal switch between 6DJ8 / 12DJ8. The Seimens E88CC glowed like the sun lol. Tough tubes."

Oops! My bad. Sometimes I don't see the righting on the wall! I was going to make mention of the 12DJ8 and there is or was a 7DJ8.

"This particular set was brand new Russian KT88 Mullard, noisy (intermittent, not steady) even after biasing and settling for 20 minutes. Definitely not good. A tube crapped out soon as I put signal through. They still test great, strangely (mA, gm). New power tubes should be generally quiet, apart from maybe an isolated soft pop burning off some impurity."

I wonder if you could have hung in there with these considering "They still test great" and they may have settled in after an hour or two with proper biasing. Its always a good plan to turn your bias pots all the way down before installing power tubes if your amp is the fixed bias type as the Apollo's are. You can bias them up gradually and watch for red plating and the like.