B k 707 tube tester

The meter deflects backwards when testing tubes in the upper section. The lower section is working OK. All the calibration adjustments seem to set correctly. When testing a diode like 5Y3 in the upper section it does work OK.

Any ideas would be helpful. Thanks, Tom.
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  1. Wow, I have not heard of the tester in a long time. The tester, like almost all test equipment, uses knob set parameters around a Wheatstone bridge and then the tube under test will show if it is good in the meter. If the tube works in the amplifier, but does not test good? I used to go the tube shelf and pull a good 5Y3GT tube out of it's box and stick it in the tester. Then I could see if the tester is working properly. But you don't have that option at the present time. I would think the tester has dirty controls or switches that does not let the settings to be set properly or you have a bad tester if the rectifier tube works properly.
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