>
>
>
>> measures writes ...
>>
>> ? A rheostat to adj. fil/heater potential costs under five dollars
>> wholesale. Do any MFJ-Ameritron amps have one? Would people pay a bit
>> extra for such a feature?
>>
>
>To be effective the filament rheostat would require built-in metering
>with proper RF decoupling at considerably more cost or would encourage
>semi-trained appliance operators to operate their amplifiers in a very
>unsafe manner (covers off, power on) in order to set the filament
>voltage properly.
Mouser sells submini RF chokes that have 470uH which have no resonances
in the ham bands. The 100-unit price is $0.29 ea. Test points could be
provided on the rear panel to connect a DMM to see what's what. . For
heater-type cathodes, metering is essential. However, for filament type
tubes, no filament V-meter is needed. While sending 50wpm dits, observe
the relative output meter. Back off the fil V adjust until you see a
slight decrease in P. Raise the filament voltage a tad. That is the
optimal point for maximal emissive life from a thoriated tungsten
cathode. .
>
>If you were a commercial amplifier manufacturer, with considerably more
>to lose than a bit of wire an a few resistors, what would you do ...
>build an amplifier that might require the user to replace tubes a
>couple times in 20 years of amateur operation or potentially cost the
>user his life and subject the company to a multi-million dollar
>wrongful death/product liability lawsuit?
Any idiot can get fried changing the mains fuses.
>
>A user with sufficient technical knowledge and concern over filament
>voltage issues should be able to easily add the proper rheostat or
>filament dropping resistor.
So who wants to buy a semi-kit?.
> Such a user can probably do it safely
>as well, unlike the legion of snake oil buyers.
>
Anyone who buys a grounded-grid amplifier with ''neutralization'' is
purchasing it.
cheers, Joe.
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