Kepco 615B Power Supply: The Kepco 615B is a beast of a bench test supply -- 0 to 600 volts at up to 300 milliamps, bias supply 0 to 150 volts at 5 milliamps and filament supply of 6.3 volts 10 amps.  A pair of 5R4 rectifiers are used on the B+, filtered by three 4.0uF oil filled capacitors. Three 6550's are used as the regulating elements.  B+ voltage is set by dialing a Powerstat autotransformer on the primary of the high voltage transformer.  The unit weighs about 60 pounds.