[Boatanchors] Tube Testing Weirdness

[Jacques Fortin]

Hello Dave,

Not sure why your TV-7 reacts like that, but I attached the spec sheets for
the KTW61 / CV1100.
Just hope they can help.
However, reduction of conductance value past a given maximum when the grid
bias is lowered happens with my AVO VCM-163 parametric tube tester with
tubes that are "worn" or slightly gassy.

73, Jacques, VE2JFE in Montreal

-----Message d'origine-----
De : boatanchors-bounces at mailman.qth.net
<boatanchors-bounces at mailman.qth.net> De la part de David Stinson
Envoyé : 1 février 2023 14:34
À : Boatanchors at mailman <boatanchors at mailman.qth.net>
Objet : [Boatanchors] Tube Testing Weirdness

Howdy, y'all.

I'm working on developing settings for the TV-7 tube tester so I can test
U.K.-nomenclature tubes for the Marconi R1155 receivers.

While developing a valid set-up for the
VR-100/KTW61/CV1100 (6.3V Fil, HS0-3485) and exploring bias range "B"
(because that's the range used by a close U.S. equiv, 6K7), I'm seeing an
odd behaviour.
While rotating the BIAS pot from 0 to full clockwise, the test meter climbs,
peaks and reverses, going down-scale again.  I don't see this behaviour on
6K7 or others.
Video:
https://photos.app.goo.gl/G4js8opd91N4kGTZ9

Has anyone an idea of what's happening here?

TNX OM ES 73 DE Dave AB5S