Sir Brian. . .

With due consideration of the units manuals specs, do you even want to do that?

" POWER REQUIREMENTS: 105-125 Volts AC, 50/60 cps ; drain 15 watts "

The median of the spec would be 115VAC input.

Two or 3 options:

However if being my task to do, I would be using a 6.3 VAC or 12.6 VAC filament transformer.

That unit gets its primary wired across the AC line thru the switch, then its separate
6.3 VAC /12.6 VAC secondary winding is wired series opposing with the primary winding of the
units original power transformer, so the the end result is an actual decrease of the primary applied
voltage by that 6.3 VAC /or / 12VAC amount.

If you accidentally have the filament transformers winding installed series adding, you wil be having the
transformer putting out either 6.3 VAC or 12.6 VAC TOO MUCH, so reverse its secondary windings leads.

Since the primary current on the power transformer is merely ~125 ma, a dinky filament transformer
with the puny spec of only 500 ma on its secondary winding would still be overkill.

The end effect being as if you were using either 117VAC or 112VAC line voltage input.

Option two would be to use a series power resistor inline with the original power transformer primary.

Use a 10 0hm 5 watt power resistor to do the brunt of the power dissipation work and then shunt across it with a lower wattage
resistor to be able to then " fine tune" in the voltage to your desired 115 VAC equivalent input voltage.

That trimming resistors ballpark value is 27 ohms at 1 watt.

The last option was the use of a series capacitor in the line, and since we are dealing with but a mere 1 watt of
power needing to be dissipated . . . . is it even worth the consideration ?

73's de Edd

The things that come to those that wait, just may be the few things left by those who got there FIRST.