...definitely!
12.6Vdc is just an indication that the correct amunt of current is flowing
there. Don't forget : what woks is P=I^2 and this defines the temperature.
Even the Volt is in essence derived from a current function.
While on the subject: modern switchers don't.give a damn whether they start in
current mode or in voltage mode so that is a moot point.
What is more important,is that you can use DC heating only on indirectly heated
tubed, which are intrinsically more tolerant about heating voltages than
directly heated types
At Tadiran , many.years
ago, we modified kW amplifiers for the GRC -106 to regulated heating voltage
foe a pair of 4CX350, reasoning that in vehicular use, it would improve
something, lifetime or performance... It didn't do anything when the operating
voltages ran from 22 to 32 volts. The only bright point was that it saved
filaments if the vehicle's generator's voltage regulator gave out. The voltage
could the rise to 40, 45 volts.
Worth it on a mains based amplifier with a ±10% variation?.....
-------- Original message --------
From: Steve Wright <stevewrightnz@gmail.com>
Date:
To: amps@contesting.com
Subject: Re: [Amps] Regulated filament current
On 05/09/15 04:00,
nemo zilch <nemozilch@gmail.com>
wrote:
> My inclination is to adjust the current so that the
> voltage across the tube is 12.6 volts. Does this seem like the correct
> thing to do?
>
I was looking at similar using a programmable switching supply. Once
the tube warms up fully, the current will normally drop off - except in
your case it won't be doing that. Also, if "other" undefined RF
conditions cause the heat in the tube to drop then I think you might
discover some uncharted territory the tube designers never imagined.
Constant current heat-up time will be longer than constant voltage as well.
Any it has to be asked, why? Just simply cold-start the filament in the
traditional manner. It's robust and inexpensive, and it doesn't provoke
the designers into adding another chapter to their do's and don'ts for
this device.
Steve
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