>
>
>
>On Sun, 31 Jan 1999 07:59:22 -0600 "Monty Taylor"
><montytaylor@texoma.net> writes:
>>
>>I have just reduced my filament voltage on the 3-500Z's in my Linear
>>from
>>5.75 volts to 5.00 volts, added 40 ohms in the primary of the
>>transformer,
>>with no load or drive.
>
>
> If I drive the amp to 600ma, for example, what
>>is an
>>acceptable voltage drop that could I expect and the ramifications of
>>such a
>>drop. The secondary filament leads are only six inches long and
>>appear to
>>be #10 or #8 stranded wire. The transformer previously supplied the
>>current
>>without getting warm. The reason for the high filament voltage is due
>>to
>>the 248 VAC furnished by the local electric utility.
>
>With a stiff 240V line the voltage drop caused by key down loading should
>not exceed a few percent. You have up to 5% to play with with a minimum
>of 4.75V. You can always adjust the resistor values to compensate but may
>not be worth the effort unless you do a lot of key down operation such as
>RTTY, etc.
>
? As I understand it, mode of operation does not affect the emissive
life of a thoriated tungsten cathode. Emissive life varies as a function
of (E2/E1)^23.4. For instance, if filiament potential is reduced from
5v to 4.75v, emissive life increases 3.3x. However, the fil. V must be
kept slightly above the level where output begins to drop.
- cheers, Carl.
Rich...
R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
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