> There are, however, DEC products other than the RK05 which had different > transformers for 50 Hz and 60 Hz. For example, the H771 power supply used > in the RX01 and RX02. There were three H771 models, The H771A for 90-132 > VAC 60 Hz, The H771C for 90-132 VAC 50 Hz, and the H771D for 180-264 VAC 50 > Hz. The H771A uses a transformer rated for 60 Hz. The H771C and H771D both > use the same 50 Hz rated transformer, with different wiring. The H771C and > H771D also require one of two different wiring harnesses to cover the > entire mains voltage range, e.g., 90-120 VAC vs 100-132 VAC for the H771C, > or twice those voltages for the H771D.
IIRC that's a ferroresonant transformer (with a capacitor to resonate one of the windings to a harmonic of the power line frequency), so it's not surprising it has to be changed for 50Hz or 60Hz input. -tony
