Blown Driver Tube

[drewh1]

Have been happily listening to my Kaiju and started to hear really great things from the EML tubes as they have started to break in a bit.

Then, a spark in the left channel driver tube, crunchy sound in left speaker and nothing.  The glass in the tube is  cracked. I switched the other tube in and the channel works fine otherwise, so my hope is it is just a defective tube.  I did not run it long, just checked the operation and shut it down again.

Can I get some feedback and a replacement tube if appropriate?  thanks.  Let me know if I should be rechecking voltages, though I am certain everything tested fine.

[drewh1]

So I checked the voltages on the driver tube circuit boards.

Ia - 531  and 530 
Oa - 298.8 and 299

rechecked 46u and reset to 175  it was a bit high.
                 32u and reset to 175 also high

So although I am certain I adjusted the voltage to 175 when I originally set up the amp, both of these values were in the 185 to 190 volt range.

[ebag4]

Good to know Drew, I will recheck mine.  I did note during the build that when I originally checked the IA voltage I was a bit low, however once the amp was complete with Tubes the voltages were dead on.

Best,
Ed

[Doc B.]

10V high is nothing to be concerned about and the voltages do move around a bit. Re the tube, we will send you a replacement. But I also want to warn that a tube is only going to get cracked like that if it it is being forced into or out of a socket or dropped. As soon as the crack forms the tube is toast, so the crack must have happened just before it blew. It would not have survived the first firing up of the amp if it arrived cracked.

[drewh1]

Doc - Thanks for the input on the voltages. However,  I did not move the tubes after the original installation, so contrary to your comment it was not dropped or forced (unless there is a poltergeist). The tubes had been in place for at least a week and half before sparking and falling apart. The other tube seems fine.

I appreciate the replacement tube, I already contacted Joshua and he wanted me to send the tube back. I sent him a photo instead, hope that suffices. it is really not worth sending a broken tube back.

[Rocketman248]

I wonder if there was a small scratch or other defect in the glass that turned into a crack after some heat cycling. 

[drewh1]

Hey Nick. Thanks for the comment. There certainly was some defect but I guess I'll never know for sure. Bottlehead is sending a replacement. First time I had anything like this happen.

Wondering if you have experience with katatsuki tubes. They get great reviews though expensive here in the states