POWER TO AN OBSOLETE MANTRIP SAFETY LIGHT SWITCH SHORTED TO THE IRON HOUSING. THE INSULATION ON THE WIRE CAUGHT FIRE AND THE SHORT CIRCUIT BLEW 250 AMP DEFUSES. THIS RESULTED IN THE BRAKE SETT ING ON HOIST. CAGE HAD 14 EMPLOYEES ON IT. THE BAD WIRES WERE ISOLATED AND FUSES WERE REPLACED AND MEN WERE HOISTED TO SURFACE. POWER DISCONNECTED FROM SOURCE AND FROM SWITCHES AND REMOVED.