Power Tube Failure

@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.

Amplitrex Tube Test System comes with all these tubes pre loaded. Works well once you have the basics in hand. Owner Chirs great to work with. Tubes drift and when you want ones that closely match or you think are kaput this delivers. It's good to test all your tubes once in a while before....(evil laugh).

@wsrrsw 

+1 Amplitrex. I have used one, it does an excellent job measuring many parameters. 

I own an Amplitrex and it does measure a lot of parameters, displays all the values as well as the expected values, and it even gives a rough overall evaluation, such as bad, weak, etc.  It is virtually idiot proof--select the tube from a dropdown menu and it will tell you which socket to use, it will warm up the tube for the proper time before running the test and it will then give the results.  Because it tests at full power, it gives a more honest assessment than most other tube testers.  If you are really ambitious, you can hook it up to a laptop to actually curve trace the tube.  It may take some expertise to interpret the curve tracing result, but, that is the way to match tube.  The BIG bad news is that it is expensive.

The other tube tester that gets raves from serious users is the eTracer.  This can be gotten with various additional features that allow for testing of very high power tubes and for convenience in not having to manually adjust settings (Amplitrex also does not require any manual settings) and it even comes in kit form for someone who wants to save money (the kit is supposedly difficult to assemble).  I know a serious tube guy with literally dozens of tube testers and this is his favorite (he owns two Amplitrex among his collection).

It’s a tube. I’d not be concerned.