Ricoh SP 8400DN Field Service Manual page 1435

7.Detailed Descriptions
LDB
LD control circuit which drives the laser diode by a universal driver.
BCU
Controls the engine, as well as printer engine sensors, motors and solenoids (the BCU has the IOB functions).
IPU
Processes digital signals by an IPU.
OPU
Controls the control panel.
HVP
Generates the high-voltage power (Charge, Development, Transfer, Separation) required for process control.
PSU
Generates DC power from a commercial AC power supply, and supplies it to each control circuit. Comprises an
A/C drive circuit for controlling the fusing lamp.
Feed tray dehumidifier heater, PCDU anti-condensation heater
Circuit configuration
If a heater is used in the main machine, it is required that the harness from the heater sub-board is connected to the
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