Brother MFC 1870MC, Service Manual, Page: 42 / 217

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30
3.5 Power Supply PCB
The power supply uses the switching regulation system to generate DC power (+25V and
+8V) from a commercial AC power supply.
The +25V source is stabilized and fed to the motor and solenoid for feeding documents and
recording paper, the main PCB, and also fed to the CIS LED array.
The +8V source is not stabilized and fed to the speaker. It is also fed to the main PCB where
the 3-terminal regulator eliminates unstabilized components of the +8V source to generate
stab5V source. The +5V source is fed to the logic, control panel, recording head, and
sensors.
Power Supply Circuit
Fuse
Lightning
Surge
Absorption
Circuit
Link
Filter
Rectifier
Circuit
Commercial
AC Power Line
Output Feedback
25 V
Output
Circuit
8 V
Output
Circuit
8 V
25 V
Oscillator
Circuit
Main PCB