HP 1200 Service Manual - Page 64

Power system on ECU The AC, DC, and high-voltage power supply circuits are all contained within the ECU. AC power distribution The AC power circuitry supplies AC voltage whenever the power cord is connected to the AC power source. AC voltage is distributed to the DC power supply circuitry and to the AC driver circuitry, which controls AC voltage to the fuser assembly heating element. DC power distribution The DC power distribution circuitry, located on the ECU, distributes +3.3 Vdc, +5 Vdc, and +24 Vdc as follows: ! +3.3 Vdc: Formatter Laser/beam detect circuitry ECU Photosensors ! +5 Vdc: Formatter ECU Laser/beam detect circuitry ! +24 Vdc: Motor Exhaust fan Laser/scanner motor Document scanner motor Solenoid Formatter (routing only) High voltage power supply Fuser safety circuit Overcurrent/overvoltage There are two overvoltage devices in this printer: ! Fuse F101 provides overcurrent protection for the fusing system circuitry. Checking or replacing the fuse requires the removal of the ECU. Fuse F102 provides overcurrent protection to the printer DC power supply circuitry. ! In addition, the +24 Vdc and +3.3 Vdc power circuitry contains an overcurrent protection circuit that automatically shuts off the output voltage when an overcurrent condition occurs as a result of a short or an abnormal voltage on the load side. 62 Chapter 4 - Operational overview EN