On Sun, 31 Jan 1999 10:40:44 -0800 Rich Measures <measures@vc.net>
writes:
>
>
>
>>
>>
>>
>>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.
As I understand it you did not understand my post. If anyone else has
that problem I will be glad to clarify.
Cheers also
Carl KM1H
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
>
>
>--
>FAQ on WWW: http://www.contesting.com/ampfaq.html
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>
>
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