Porto-Arc rectifier
3/4-front view of selenium* rectifier lamphouse power supply for the RCA Arc 400 carbon-arc 16mm movie projector, showing the current control. A fan located at the base of the power supply forces air upward to cool the transformer and rectifier stack.
This nearly-60 lb. (27 kg.) chunk of mostly iron and steel outputs 30 amperes at 28 volts, or about 840 watts, when carbons are properly aligned and the current control is adjusted to achieve the specified current.
*The specification plate on the back says "selenium" but it looks like it was retrofitted with a pair of high-current silicon diodes mounted in heat sinks along with a large electrolytic capacitor to smooth the DC output.
Porto-Arc rectifier
3/4-front view of selenium* rectifier lamphouse power supply for the RCA Arc 400 carbon-arc 16mm movie projector, showing the current control. A fan located at the base of the power supply forces air upward to cool the transformer and rectifier stack.
This nearly-60 lb. (27 kg.) chunk of mostly iron and steel outputs 30 amperes at 28 volts, or about 840 watts, when carbons are properly aligned and the current control is adjusted to achieve the specified current.
*The specification plate on the back says "selenium" but it looks like it was retrofitted with a pair of high-current silicon diodes mounted in heat sinks along with a large electrolytic capacitor to smooth the DC output.