[Boatanchors] 539 tube tester problem

[hwhall at compuserve.com]

When you were measuring the 6L6 (etc.) was the tester left on all that time, maybe with the 6L6 on too?
I once noticed that my Hickok 6000A would give different readings when it has been on a long time and gotten really warm. I think many of these testers were meant to be used intermittently, just long enough to test a few tubes, & not left running long enough to get hot.

I've seen testers where someone installed a cooling fan & opening, presumably to cure the drifting readings when left on a long time.
WayneWB4OGM

-----Original Message-----
From: Yongsurk Lee, HL1FB <yonglee at yonsei.ac.kr>
To: boatanchors at mailman.qth.net
Sent: Wed, Aug 5, 2020 6:38 am
Subject: [Boatanchors] 539 tube tester problem

This is HL1FB/WW6N in Seoul, Korea. I have been repairing tube equipments
here in Korea for many years as a hobby. I successfully repaired about 200
TV-7s, TV-2s and some Hickok tube testers.
I had a Hickok 539A and a 539B which I could not find the exact cause of
the problem. When I test tubes like 6L6, the test values increase as time
goes by. Right after turn on it may indicates 6000 but after 30 minutes it
goes up to 8000, then 9000.....
I tried 50VAC and 10k ohm in series and applied between plate and cathode
at different ranges. They all indicate correct values with no increase with
time. Grid signal voltage is contant with time.
Do you have some idea what can be problem?
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