> The following may be stimulating --- my Henry Ultra metering
> does read the filament voltage. But, so far as I know, there
> is no rheostat in sight to adjust same.
R-617 in the 8-K Ultra power supply section. is a power resistor in
series with one side of the primary of the filament transformer. It serves
two purposes...to limit filament inrush current and to allow filament
voltage to be adjusted if necessary by selecting the proper value
for your particular line voltage. If you specify the line voltage at your
QTH when you order the amp, the resistor is installed at the factory
of a proper value to suit. If not, the value is selected based on a line
voltage of 230v.
Not as convenient as a rheostat or multi-position switch, (4-K Ultra) but
you only have to do this once each time you change QTH's.
I adjust the filament voltage on my 3CX3000A7 amps by metering at
the filament pins and adjusting the series resistor to 7.49 volts. I then
calibrate my filament voltmeter to read the same.
(((73)))
Phil, K5PC
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