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Original Message

Heathkit tube tester

Posted by 2bkurius on June 24, 2011 at 19:36:23:

I recently received an old Heathkit tube tester. I was testing some 300B tubes that were only a couple of years old and are only on a few hours a week. The tubes tested in the middle, neither good nor bad. I thought they would test better. The chart said to set the plate setting at 21? but if I moved the plate setting to 30? they tested good and when I moved it to 40? they tested 100 percent(?). Could someone tell me what this plate setting is adjusting and if this seems like a normal reading for a 300B that is only a couple of years old? Thanks in advance.