Máximo EA1DDO_HK1H wrote:
> I´ve been told that I can use DC for filaments (instead of AC), Is that true?
> If it is true, Can I use switching power supply for filaments?
> Tubes GU81 needs 12.6 v and around 10A, I could use 2 x 12.6 25A switching
> power supply in parallel with two chokes.
> Is that correct?
> Is there any difference to use AC or DC for filaments? (in grounded grid )
You can always use DC on an indirectly heated cathode, but with a directly
heated filament you
must consider the fact that one end of the "cathode" will have 12.6 Volts more
or less cathode to
grid bias than the other, this will cause one half of the filament wire to emit
more electrons than
the other. Generally this is to be avoided. It can reduce the life of the
filament, as the
emissive current must be added to the filament current in that part of the
filament causing that
part to operate at a higher (than normal) temperature.
I do not know if this would be a problem with GU81Ms or not.
It is next to impossible to parallel two switching supplies without having one
regulator circuit
control both supplies, they will not "share" the load without a pair of power
loosing combining
resistors.
--
73 Ron KA4INM - All E-mail sent to this address shall linger in the Google
cloud forever!
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