Power tube measuring 0ma cathode current?

[ed the yak]

I was checking the bias on my amp earlier, and had my Bias King Pro measuring the cathode current on the tubes. One of the tubes measured 0ma. I tried switching the two tubes I was measuring to see if it was a problem with the Bias King, and the same tube measured 0ma in the other socket. All three of the other tubes gave good readings. All the tubes light up, and appear to be operating normally, and the amp sounds fine.. It's by backup, but I've been using it at band practice lately. Has anybody ever had something like this happen?

 

[MrDan666]

I was checking the bias on my amp earlier, and had my Bias King Pro measuring the cathode current on the tubes. One of the tubes measured 0ma. I tried switching the two tubes I was measuring to see if it was a problem with the Bias King, and the same tube measured 0ma in the other socket. All three of the other tubes gave good readings. All the tubes light up, and appear to be operating normally, and the amp sounds fine.. It's by backup, but I've been using it at band practice lately. Has anybody ever had something like this happen?

Sounds like a dodgy tube..

If the tube is reading 0mA in whichever socket you plug it into, then it sounds like the tube is the problem.

 

[JerryP]

If one tube reads zero and the reading follows the tube and doesn't stay with a particular tube socket then you have a bad tube.
Jerry

 

[ed the yak]

Thanks, I figured it would probably be that. I got about $250 worth of tubes from the tube store back in June, and so far, A NOS Jan/Phillips 12ax7, and a Chinese 12ax7 that I ordered were both microphonic right out of the box, and now an EL34 went. The power tubes haven't even been played much, they were in my backup amp, that I've been playing after a KT88 blew in my Ultralead. I still have 4 more Chinese 12ax7's to try, I'm hoping those all work fine, but I'm not optimistic right now. I know tubes go bad, but this seems like a bit much.