A cheap trick I use for filament current limiting was
"borrowed" from Henry.
If your filament voltage is a bit high, or you have a tapped
filament transformer,
or better yet, a variac, just insert a power resistor in one
leg of the filament transformer
primary. (c. 20-25 ohms, or as required) This will limit
inrush current and set the filament
voltage to the proper value. (two birds with one stone)
Since it is hard-wired into the circuit,
there are no moving parts, or contacts to "weld" in the
middle of a contest. As to size, I just
select a wattage value that just barely gets warm.
Over-engineering in this area is inexpensive
and prudent.
(((73)))
Phil, K5PC
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