HP 8550 Service Manual - Page 237

Power supply Figure 131 and figure 132 show the distribution of power inside the copy module. The AC power sent to the copy module main power supply is turned on and off by the copy module rear power switch (MSW1). When the copy module main power supply PCB is supplied with AC power, +5V is generated. When the control panel power supply soft switch is turned on, the power cut relay ON signal (RL1ON) is sent through the reader controller PCB to turn on the power cut relay, thereby supplying the printer unit with AC power. The copy module main power supply PCB generates +5V, +5VA, +5.2V, 12V, +15V, +24V, and +40V. Power saving function The copy module is provided with "low power mode" and "auto power save mode." Table 65. Power saving function Copy module rear power State of power switch Low-power mode ON Auto power save ON mode Control panel power soft switch ON ON Fuser assembly OFF Variable temperature control l Low power mode-In low power mode, the fusing assembly is turned off to reduce power consumption. l Auto power save mode-In auto power save mode, the fuser assembly remains on; however, the temperature control target is lowered to reduce power consumption. Protective function The copy module main power supply PCB is equipped with an overcurrent protective function and an overvoltage protective function which will automatically shut off power to prevent damage to the power supply circuit if an overcurrent or an overvoltage occurs as a result of a fault in any of the loads (for example, short circuit). To reset the copy module, turn off the control panel power supply soft switch, turn off the copy module rear power switch, disconnect the power plug, remove the cause of activation, and turn on the power once again. The protection circuit may be reset by turning off the copy EN Copy module 235