Hi,

I want to test a 12AX7 on my Stark 9-66 tester. Setting is completely different for both diodes (need to reset all switches for testing second diode).

Questions are:

- Do I have to remove tube before reseting switches to test second diode to prevent damaging tube?

- Is it normal when testing for gas, that result is different for both diodes?

- Do I have to test for shorts on both diode, or only one test is sufficient?

Thanks!
J-F

:Hi,
:
:I want to test a 12AX7 on my Stark 9-66 tester. Setting is completely different for both diodes (need to reset all switches for testing second diode).
:
:Questions are:
:
:- Do I have to remove tube before reseting switches to test second diode to prevent damaging tube?
:
:- Is it normal when testing for gas, that result is different for both diodes?
:
:- Do I have to test for shorts on both diode, or only one test is sufficient?
:
:Thanks!
:J-F
:
There are no diodes in the 12AX7; it is dual triode. I always remove the tube before changing settings for the second section. I had a bad experience about 35 years ago and it stuck with me.
Johnnysan-

Yes, that's right, double triode. My error... :)

Did you mean a 12AV6 ? I don't know about your tube tester. But on my Hickoc 800 It is best to pull the tube then set the knobs and switches for each test.

If the settings are obvious (filament, etc.), and plate current is only applied when the merit button is pressed, you may change settings for each side of the dual triode without removing the tube. Sometimes, when there are dual taps for a filament, it is wise to turn the filament control down to 0 volts while making switch changes. When testing a tube like the 35W4 where there are two unequal sections of the filament, it is wise to leave the filament control set at 0 until all other settings have been made. There are other tubes, too, that have internal connections between two pins, and if your tester is like my EICO 625, you will be throwing pin switches up and down from center. If you throw one lever down and the other lever is up for two pins that are internally connected, and filament voltage is applied, you will short the tester or burn the connection within the tube.

If you are unsure of how your tester operates or how elements are connected within a tube, it is best to remove the tube being tested whenever switch adjustments are being made.

T.