• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

Another Heater Wiring Question

Apologies for the delay, it took a while to find my two 866A's... I powered them up using a bench PSU and got similar results for both valves. Both pulled nearly 6A when first switched on, then settled to 4.6A @ 2.5v bang on after 5 minutes, so your reading of 4.4A isn't too far off. It might tax your tfmr a bit at first but see how you go.

Andy.