I’m about finished building a K4040 amplifier. When I powered up the (no load) voltage of the secondary heater windings was 7.2V AC; I was unhappy about plugging in the valves on that much overvoltage.
The mains here is around 240V and both voltage selector links are to ‘D’. If I measure the voltage on the other input tappings they are about right.
I tried loading one of the heater secondaries with a 4.5 ohm resistor, ~1.6 Amps, but it made little difference to the voltage.
Currently I’m using an old transformer to drop the input voltage to about 220 V (with the voltage selector links still set to 245) and this gives a heater voltage with everything plugged in of 6.2 - 6.25. However this isn’t a long term solution.
Advice please. Particularly in the early stages of commissioning where you plug in only the 3 small valves their heaters would be getting the full 7.2 volts.