22-07-2013, 03:03 PM
Don't forget that in most designs the mains transformer will be run fairly close to saturating the core at the highest specified mains voltage. At this point, even a slight increase in primary voltage will give a disproportionately large increase in current as the core enters saturation. You can check this by monitoring the mains current while adjusting the voltage with a variac. The effect is even more dramatic if you can remove the load from the transformer (unplug all the valves) so that you are looking at just the magnetising current.
Some 220V sets may be fine in the UK, especially if your mains is on the low side. Others may not. A tiny transformer will serve to buck the voltage. For example if you are using a 240V to 20V TX to buck 20V on a radio rated at 100W, the buck TX need only be rated at 8.3VA.
Some 220V sets may be fine in the UK, especially if your mains is on the low side. Others may not. A tiny transformer will serve to buck the voltage. For example if you are using a 240V to 20V TX to buck 20V on a radio rated at 100W, the buck TX need only be rated at 8.3VA.
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
