Main Pcb - Brother IntelliFax-3550 Service Manual

3.2

Main PCB

The main PCB, which is the nucleus controlling the entire operation of the equipment, con-
sists of a FAX engine (ASIC), memories, MODEM, motor drive circuits, sensor detection cir-
cuitry, and analog circuits for scanning, printing, and power transmission shifting.
(MFC4450/
4550/4550plus/
6550MC/7550MC/
7650MC/9000/9500)
Modular
connector for PC interface
(RS-232C)
(FAX3550/3650/8000P/8200P)
ROMs
DRAM(s)
Extended RAM
connector
Extended I/O
connector for
optional serial
interface board
(RS-232C and
RS-422)
(MFC6550MC/7550MC/
7650MC/9000/9500)
Centronics
parallel interface
E 2 PROM(s)
MODEM
2
E PROM: Electrically Erasable Programmable Read-only Memory
DRAM: Dynamic Random Access Memory
Block Diagram of Main PCB
III – 13
Main PCB
Main motor
driver
ASIC
Image
processor
Scanner
motor driver
Amplifiers
Analog switch
operational
amplifiers
Control panel
Relay PCB
Fan 2
Main motor
Solenoid
Low-voltage
power supply
PCB
Document
sensor PCB
Scanner
motor
Speaker
NCU PCB
Hook switch
PCB