Brother MFC620CN Service Manual page 88

CHAPTER 3 THEORY OF OPERATION
This chapter gives an overview of the scanning and printing mechanisms as well as the sensors,
actuators, and control electronics. It aids in understanding the basic principles of operation as
well as locating defects for troubleshooting.
3.1 OVERVIEW ...................................................................................................................... 3-1
3.2 MECHANICAL COMPONENTS ...................................................................................... 3-2
3.2.1 Scanner Mechanism ............................................................................................ 3-5
3.2.2 Printing Mechanism ............................................................................................. 3-8
3.2.2.1 Paper pulling-in, registration, feeding and ejecting mechanisms................ 3-8
3.2.2.2 Ink supply and ink jet mechanism ............................................................. 3-11
[ 1 ] Overview.................................................................................................... 3-11
[ 2 ] Features..................................................................................................... 3-12
[ 3 ] Head/carriage unit ..................................................................................... 3-13
[ 4 ] Ink cartridges ............................................................................................. 3-20
[ 5 ] Ink refill assembly ...................................................................................... 3-22
[ 6 ] Ink supply tubes......................................................................................... 3-24
3.2.2.3 Head maintenance mechanism................................................................. 3-25
[ 1 ] Maintenance mechanism components...................................................... 3-25
[ 2 ] Maintenance unit components .................................................................. 3-25
[ 3 ] Head capping mechanism......................................................................... 3-27
[ 4 ] Purge mechanism...................................................................................... 3-28
3.2.2.4 Carriage drive mechanism ........................................................................ 3-37
3.2.3 Sensors and Actuators ...................................................................................... 3-39
3.3 CONTROL ELECTRONICS .......................................................................................... 3-42
3.3.1 Components ...................................................................................................... 3-42
CONTENTS
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