Ozzy 2005 wrote in news:sJ_0e.2010$T_6.286
@fe12.lga:

Just got a 5814 / 12AU7 in and tested it on my tube tester according to
the setup instructions on the tube list that comes with the tester.
Sencore Mighty Mite II, TC 114. Of course the tube was sold as NOS,
however, an odd thing happened when I tested it. Both sides fail.

There are no shorts or leakage and my tester was calibrated, albeit a
year ago, and tests all my other tubes, 12AX7, 12AT7, EL34, EL84, 6L6GC
fine and has properly indicated new and used tubes as well as shorts.

So my questions is this, might the setup data be wrong. All that
changes from a 12AX7 is the plate load goes down one click and even
testing it as a 12AX7 it only passes minimally. Could there be some
reason other than DECEPTION on the part of the seller as to why this
tube is failing. HYPE (grandiose marketing) in my book is as good as
deception. We're talking this tube has seen at least 1,000 hours to not
be in the green on my tester. That far exceeds using a tube briefly not
liking it and still claiming it's NOS.



While the Sencore is not the best in the world it is OK. I have tested
many tubes and never have I seen a case where a tube was good when it
measured bad on that tester.

I have seen the converse no matter what tester I used.

Try bumping up the heater voltage by one click and see if it makes a
difference. If it doesn't, then I would say you have a bad one. I have
seen brand new tubes be bad. I don't know why some tubes fail at normal
heater voltages but pass when slightly higher than normal. Some call that
a bad tube I suppose.

If you are wondering if the tester is correct, the only reliable way to
tell is to test another 12ax7. Anything else is quessing. You should
check for socket corrosion and loose pins.

r