[Techlunch] Wait! There's more!

[Dennis Gibson]

Gday,

Still on the subject of the RF heater job, I have measured the filament and the voltage is
within the specs (9.5V 5%) at 9.3V but the current  at 4A is questionable!  I don't have a
spec for it, but it is 50Hz AC from a transformer and the winding is rated at 23A!

Now I reckon that the filament has gone high res over time, explaining the
gradual demise of the idle plate current (2A in the 70's, 1.2A in the 90's, 1/2 A in the 00's)

Other 10's of kW tubes in my EIMAC catalogue all have filament currents tn the 10's of
amps, (200A) even thorated filament types.  Now thw schematic shows a direct heated
cathode, but the manual describes an indirectly heated one.  Take your pick.

Now, does 4A sound right, or would 20A be more like it bearing in mind the 23A transformer?

OBTW please reply to the two groups, not to me directly (don't even copy to me) as that
way everyone shares in the collective wisdom!

Cheers,
DG
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Dennis Gibson, Electronics Unit
Research School of Physical Sciences & Engineering
Australian National University, Canberra, ACT 0200
Australia

Ph: (02) 6125 2607  [Intl: +61 2 6125 2607]
Fx: (02) 6125 4433  [Intl: +61 2 6125 4433]

Email: dennis.gibson@anu.edu.au

(VK1DG)
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