12vac filament PT

[dude]

Not loaded this PT, 6.3-0-6.3 reads 7.3vac on each leg, can I assume that it's higher because of no load and with a load would it most likely be 6.3vac?


al

[shooter]

can I assume

absolutely, but at some point ya gotta prove it 

[PRR]

Un-sag may be 5% on big iron, 20% on small iron.

So it will likely be closer to 6.3V when fully loaded.

I would just put a large tube on it. 7.3V does not make a 6.3V tube blow-up like flash powder; if you kept it up, it would reduce heater life from 10,000 hours to 1,000 hours. However everything sags, so it won't be 7.3V. If it comes to 6.0 to 6.6V, rock on.

(BTW: I just saw a Scott hifi amp with 12.6V heaters worked at 7V! It should be noted that they also worked near 0.25mA cathode current, far less than most designs. These amps still work 57 years later.)