Tube dead on arrival?

[timrobertson100]

On finishing a new build I had a red plating 6v6 from a matched pair with the bias down super low (startup procedure).
Swapped the tubes over the red platting followed the tube. Swapped in a known good pair and all was fine, so I brought up the bias.

It's my first experience of a tube being seemingly dead on arrival - curious if anyone else experienced that?

[10thTx]

Yes

[Stevem]

Just because the tube was red plating does not mean it was not working, it could have been way out of spec, in fact I am questioning why it did not pop the amps fuse on you if it was red plating enough.

Maybe another 300mv of - bias voltage might have had that tube idling just fine.

[timrobertson100]

Thanks, 10thTx, Stevem

I wondered about that. I caught it quickly within seconds and plugged in the bias master which reported the tube pulling upwards of 150mA. At that point, I went for the other tubes.
I just tried again out of curiosity and it's the same - the current just ramps up... a dead tube, right?

[rdavy]

I just recently had a brand new 6V6 screen grid internally short to ground. Very frustrating because I thought I had done something wrong.

[pjd3]

The jury isn't totally out for the exact cause but I just bought my first pair of current production tubes (JJ 6V6S's) after using only NOS tubes my whole life. ut

As I was gradually increasing the bias current to near 70% emissions the 6.3vac heater resistors smoked up and burnt. The amps output waveform went flat and I found this had blown a fuse on the primary side of the PT. Kinda scared me. Thankfully, I put the original Sylvania NOS 6V6's back in that I had used with no issues for 2 years and all was well once again. I have no course than to put the cause of this problem onto the new JJ 6V6's. I'm a senior electronic tech by day and take safety and component specifications seriously.
I had heard good things about the JJ 6V6S's and was very interested in giving them a whirl.

Lets see what the vendor tells me - I sent them a descriptive overview of the problem that occurred and asked it they would work with me to address the problem. I even gave the link the Amp Garage thread I created where I got alot of good feedback from others experience with similar issues.

Yup, sometimes we get a dud I guess.
Best,
Phil Donovan

[Reeltarded]

JJ is no longer a trusted brand. EH from 3-4 years ago is the last best tube I know of.

[TUBEDUDE]

C'mon Western Electric!
When will we see the tubes that America needs now!

[Reeltarded]

Asking for new tubes is akin to googling for whip grade leather.