Tube flash

I've had tubes flash, cause damage, and not only measure perfectly fine, but go on and lead a typical, long, quiet suburban life.

Culling tubes that test poorly in their infancy is certainly wise practice. While tubes that get through boot camp obviously will lend a higher degree of confidence, let's not be lulled into a false sense of security. Tubes do hiccup and fail, and sometimes collateral damage results. The old investment adage "past performance is no indication of future results" rings true with vacuum tubes as well.

"How old was the tube that failed? Have you contacted Kevin in regards to the tube's failure (and possible warranty)? Did the same thing happen more than once? You mentioned, "the problem has continued”

No I haven’t contacted Upscale…the first tube that failed was probably 4 – 6 months old. As I mentioned before, this is the fourth of eight tubes that has failed. I should have taken notes, so I really don’t remember when the tubes failed, which positions failed, etc. I do know it has happened in both amps.

"(why I ask)".

“Why” the problem continues is what I am wondering as well.

"Next time you talk to CJ ask them what the bias setting programmed into the amp actually is. After they tell you ask them what the bias setting is in the 6550 model. Then find out if they actually checked the bias in your amps with your tubes in it as opposed to just noting the tubes and the little LED were working."

Now that I know a little more specifically what to ask, I will. Thanks for the advice. I do know that they checked the bias in the amps with my tubes the last time they were in for service. That’s how they found the problem (the amp was blowing fuses and my tester was not detecting a bad tube).

"If you have a techie nearby you might ask him to check and see what the bias actually is."

Actually, Bill Thalmann, whom I believe may have designed the Premier 12’s when he worked for CJ, also has his shop in my area. So I may take it to him the next time it happens.

See Emission labs' website under advanced tech notes about tube flash. Something about inrush current and new, high transconductance tube along with the wrong grid resistor value.

And may powdered sugar fall gently upon your ears tonight

Unless I'm on the wrong site I see no reference to what you refer to. Can you give me a link?

Jaff keep looking, Its in there buried