HP LASERJET ENTERPRISE M855 - 1 Theory of operation

Table of contents
1 Theory of operation ........................................................................................................................................... 1
Basic operation ..................................................................................................................................... 2
Sequence of operation ......................................................................................................... 3
Normal sequence of operation ............................................................................ 3
Formatter-control system ..................................................................................................................... 4
Formatter hardware ............................................................................................................. 4
Sleep mode ......................................................................................................... 4
Input/output ......................................................................................................... 5
CPU ..................................................................................................................... 5
Memory ............................................................................................................... 5
Firmware ............................................................................................................. 5
Nonvolatile memory ............................................................................................ 5
PJL overview ....................................................................................................... 6
PML ..................................................................................................................... 6
Control panel ....................................................................................................................... 6
Engine-control system .......................................................................................................................... 7
DC controller ........................................................................................................................ 8
Motors ............................................................................................................... 12
Fans .................................................................................................................. 14
Automatic damp paper detection ...................................................................... 14
Low-voltage power supply ................................................................................................. 15
Over-current/over-voltage protection ................................................................ 17
Sleep mode operation ....................................................................................... 18
High-voltage power supply ................................................................................................ 19
Fuser bias ......................................................................................................... 20
Fuser-control circuit ........................................................................................................... 21
Fuser heater protection ..................................................................................... 23
Fuser identification ............................................................................................ 25
Fuser-life detection ............................................................................................ 25
Laser/scanner system ........................................................................................................................ 26
Image-formation system ..................................................................................................................... 27
Image-formation process ................................................................................................... 28
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