[AMPS] 3-500Z filament voltage

km1h@juno.com km1h@juno.com
Sun, 31 Jan 1999 16:44:31 -0500




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  
>
>
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>

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