HP M425

Table of contents
1 Theory of operation .......................................................................................................... 1
Basic operation ........................................................................................................................ 2
Major product systems ............................................................................................... 2
Product components .................................................................................................. 3
Sequence of operation ............................................................................................... 4
Engine control system ............................................................................................................... 6
DC controller ............................................................................................................ 7
Motor control ............................................................................................................ 9
Fan control ............................................................................................................. 10
High-voltage power supply ....................................................................................... 11
Fuser control circuit .................................................................................. 12
Fuser temperature control ........................................................... 13
Fuser protection function ............................................................ 14
Fuser failure detection ................................................................ 14
Low-voltage power supply ........................................................................................ 16
Protective function .................................................................................... 16
Safety ..................................................................................................... 17
Low-voltage power supply unit failure detection ............................................ 17
Laser scanner system .............................................................................................................. 18
Laser failure detection .............................................................................................. 19
Image-formation system ........................................................................................................... 20
Image-formation process .......................................................................................... 21
Latent-image formation stage .................................................................................... 22
Step 1: Primary charging .......................................................................... 22
Step 2: Laser-beam exposure ..................................................................... 23
Developing stage .................................................................................................... 23
Step 3: Development ................................................................................ 23
Transfer stage ......................................................................................................... 24
Step 4: Transfer ....................................................................................... 24
Step 5: Separation ................................................................................... 24
Fusing stage ........................................................................................................... 25
Step 6: Fusing ......................................................................................... 25
ENWW v