>
>I have been using the Triac soft start wall switch unit as the filament
>switch in an amp which used 4-1000 and later an 8877 for 15 years with no
>problems.
A problem is that because of the non-sinusoidal waveshape, only a true
RMS voltmeter will accurately measure fil. volts. Also, the 4-1000A and
8877 specs do not indicate a requirement to limit inrush current.
cheers, Dan
----------------
>
>Mark Marsden wrote:
>
>> >
>> >Rich says:
>> >
>> >>So when are amplifier manufacturers going to get off of their lazy
>> butts
>> >>and start building amplifiers. with a filament adj. rheostat and a
>> means
>> >>of measuring filament potential?
>> >
>> >I guess they don't because of number 1, cost, and number 2, the
>> capability
>> >of allowing people to wind up the volts - 'gee, Wilma, you get more
>> output'.
>> >
>> >Better, but even more expensive, is a regulated filament supply that is
>> >current limited so the inrush current can't exceed twice the normal
>> current,
>> >and doesn't vary with line volts. You can afford to build that sort of
>> thing
>> >into a home brew amp.......but commercially it's a no-no.
>> >
>> >73
>> >
>> >Peter G3RZP
>> >
>> Heaters are soft-started with a motor-diriven variac, or
>> get a step-start supply, but has anybody seen or tried
>> slow starting a heater using a triac and PWM control?
>>
>> Mark G4AXX
>>
>>
>>
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>>
>>
>> --
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>
>
>
>
>--
>FAQ on WWW: http://www.contesting.com/ampsfaq.html
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>
>
--
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Search: http://www.contesting.com/km9p/search.htm
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