[Boatanchors] 539 tube tester problem

[Yongsurk Lee, HL1FB]

I enountered only two Hickoks that showed this problem. Other Hickoks all
had stable reading over time.
Thanks for your advice.

On Thu, Aug 6, 2020 at 8:25 AM <hwhall at compuserve.com> wrote:

> 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.
>
> Wayne
> WB4OGM
>
> -----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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