[miniman82]

Found the same condition in my Eico tube tester recently. Most tubes it gives a pretty good test, like the common octals and all the 7 and 9 pin miniatures. But I recently installed a 9 pin and 12 pin compactron socket so I can test some late model tubes, and apparently a few have some pretty high filament demands. Like the 6LB6, it dragged the whole thing down to the point where the voltage adjust knob was nearly maxed out. Normally that wouldn't be a problem but because the emission indication circuit and filament power comes from the same transformer, it was giving me erroneous indications. You're supposed to adjust it to a mark called 'line' when testing, but these large sweep tubes draw so much current that when doing it that way I only had like 5.5 volts on the filament. Fix will be a small aux transformer that only runs the indication circuit, leaving the filament transformer to do its thing. I also may put in an actual filament volt meter, so I can be sure it's actually putting the correct voltage to the tube under test. That should give more stable and repeatable testing.