HP LaserJet Pro M402d - Page 9

Table of contents
1 Theory of operation ....................................................................................................................................... 1
Related documentation and software ................................................................................................................... 2
Basic operation ...................................................................................................................................................... 3
Sequence of operation ........................................................................................................................ 4
Engine-control system .......................................................................................................................................... 5
DC controller ........................................................................................................................................ 6
Motor control ..................................................................................................................... 8
Fan control ........................................................................................................................ 8
Low-voltage power supply .................................................................................................................. 9
Over-current/over-voltage protection ........................................................................... 10
Safety ............................................................................................................ 10
Low-voltage power supply functions ........................................................... 10
High-voltage power supply ............................................................................................................... 11
High-voltage power supply circuits ................................................................................ 12
Fuser bias ........................................................................................................................ 12
Fuser control ..................................................................................................................................... 12
Fuser circuits ................................................................................................................... 13
Fuser control functions ................................................................................................... 14
Fuser heater protection .................................................................................................. 15
Engine laser/scanner system .............................................................................................................................. 16
Laser/scanner failure detection ........................................................................................................ 17
Safety ................................................................................................................................................ 17
Image-formation process ................................................................................................................. 18
Step 1: Primary charging ................................................................................................ 21
Step 2: Laser-beam exposure ......................................................................................... 22
Step 3: Development ...................................................................................................... 22
Step 4: Transfer ............................................................................................................... 23
Step 5: Separation ........................................................................................................... 24
Step 6: Fusing .................................................................................................................. 24
Step 7: Drum cleaning ..................................................................................................... 24
Toner cartridges ................................................................................................................................ 25
Design ............................................................................................................................. 25
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