HP 8550 Service Manual - Page 240

CAUTION Accessories power supply PCB The copy module is equipped with an accessory power supply PCB for the ADF. The accessories power supply PCB receives DC power from the copy module main power supply PCB (after AC activation); +24V is sent to each load (ADF) in response to the remote signal from the reader controller PCB. As in the case of the copy module main power supply PCB and the printer unit low-voltage power supply PCB, the accessories power supply PCB is equipped with an overcurrent protective function and an overvoltage protective function to automatically cut off the output voltage to prevent damage to the power supply PCB in the event of an overcurrent or an overvoltage. To reset the accessories power supply PCB, turn off the control panel power soft switch, turn off the copy module rear power switch, disconnect the power plug, remove the cause of activation (usually a bad component or a short), and then turn on the power. To reset the copy module protection circuit, turn off the copy module rear power switch for approximately three minutes, and then turn on the copy module rear power supply and control panel power soft switch. Do not disconnect or connect cables (lattice connectors) used to connect accessories (for example, the ADF) and connectors used to connect various units while the copy module remains powered (the copy module rear power switch is on) to prevent blowing the protective fuse on the secondary side of the power supply. The ratings of the fuses used on the secondary side of the copy module main power supply and the accessories power supply are as follows: 238 Chapter 5 - Theory of operation EN