[Amps] filament supply options

[Steven Grant, W4IIV]

Hi steve
the voltage shoud be 4.8 volts for maximum tube life. 5 volts or more will cut tube life with very little benifit.
the reason AC is used has to do with biasing, 5 volts DC with this tube will affect biasing (in many amps, 5 volts is what they use to bias the tube to cut off)
btw the wattage is 75 watts.
have fun, steven

Steve Jackson <kz1x at yahoo.com> wrote:
Let's say I have a 3-500z which wants 5 volts at 15
amps for the heater. 

The spec doesn't say AC or DC -- and according to Ohm,
(given that one is 60 Hz and the other is zero Hz into
what is essentially a resistive load on the other side
of a BIG choke) it doesn't matter. 

Watts is Watts.

I have a 5 volt, DC, 20 amp, industrial-grade
switching supply. It cost $2 and weighs about 3 lbs. 
Power-factor-corrected, auto-ranging 90-255VAC input.

What do you say I use the switcher, instead of the
$58, 22 lb. transformer that would provide the same V
and I ... with poorer regulation, etc. ? 

Before someone says something about switchers and RF
noise, etc., I checked this one under load and it
doesn't put out anything I could hear. It also
provides about 4500v isolation to the AC input, and it
didn't flinch when I subjected it to a strong RF field
at 14 and 28 MHz.

What's wrong with this picture? Why aren't more
people going this route when building?


Steve KZ1X/4 ...

... who is also looking pretty seriously at that HV
switcher from Watts Unlimited







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