HP LASERJET ENTERPRISE CP4020 - Theory of Operation; Basic Operation; Engine-Control System; High-Voltage Power Supply

Table of contents
1 Theory of operation
Basic operation ..................................................................................................................................... 2
Sequence of operation ......................................................................................................... 3
Engine-control system .......................................................................................................................... 4
DC controller ........................................................................................................................ 5
Solenoids ............................................................................................................ 5
Clutches .............................................................................................................. 6
Switches .............................................................................................................. 6
Sensors ............................................................................................................... 7
Motors ................................................................................................................. 8
Fans ..................................................................................................................................... 9
High-voltage power supply ................................................................................................ 10
Low-voltage power supply ................................................................................................. 12
Overcurrent/overvoltage protection ................................................................... 13
Safety ................................................................................................................ 13
Voltage detection .............................................................................................. 13
Sleep (powersave) mode .................................................................................. 13
Low-voltage power supply failure ...................................................................... 13
Fuser control ...................................................................................................................... 14
Fuser temperature control ................................................................................. 15
Fuser sleeve temperature protection ................................................................ 15
Failure detection ................................................................................................ 16
Fuser unit identification ..................................................................................... 17
Fuser unit life detection ..................................................................................... 17
Laser/scanner system ........................................................................................................................ 18
Laser/scanner failure ......................................................................................................... 19
Protective-glass cleaners ................................................................................................... 19
Image-formation system ..................................................................................................................... 21
Image-formation process ................................................................................................... 22
Step 1: Pre-exposure ........................................................................................ 24
Step 2: Primary charging ................................................................................... 24
Step 3: Laser-beam exposure ........................................................................... 25
Step 4: Development ......................................................................................... 25
Step 5: Primary transfer .................................................................................... 26
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