HP LaserJet 4v/mv Service Manual - Page 67

AC Power Distribution The AC power circuitry supplies AC voltage whenever the power cord is connected to the AC power source and the power switch is turned ON. A toner cartridge must be installed and the front door closed before voltage is supplied to the Power Supply circuits, the DC Controller, the Main Motor, or the Fusing Assembly. Overcurrent/Overvoltage Protection There are three overvoltage /overcurrent devices in this printer: The resettable circuit breaker (CB101) shuts off AC input power to the Power Supply Unit in case of an AC overcurrent condition. To reset, remove the Upper and Right side covers and push on the small round button located directly above the ON/OFF switch. Fuse F101 shuts off AC input power to the +24V DC and +5V DC power circuits. To check or replace the fuse requires the removal of the Power Supply Unit. In addition, the +24V DC and +5V DC power circuitry contains an overcurrent protection circuit which automatically shuts off the output voltage when an overcurrent condition occurs due to a short or abnormal voltage on the load side. The protection circuit automatically resets after the input power is cycled OFF (for at least 3 minutes) then ON. Functional Overview 5-5 Functional 5 Overview