Logic And Vh Power, And Related Circuits - Brother PT-2500PC Service Manual

3.2.3

Logic and VH Power, and Related Circuits

If the AC line adapter is plugged in the machine, the power supply PCB supplies Vcc
(+5V) to the main PCB. Vcc is a power source to the logic circuitry.
The moment Vcc is supplied, the reset IC (Q2) operates to turn the RESET signal from
Low to High, starting the CPU to run. The CPU initializes its ports and then enters the
sleep mode (power-off).
Pressing the ON/OFF switch in the sleep mode causes NMI interrupt to start the CPU.
Pressing the ON/OFF switch with power on places the CPU in the sleep mode (Power
off).
To drive the mechanism, the CPU turns P83 High to turn on Q5 (FET) on the power
supply PCB, supplying VH to the thermal head, cutter motor, and tape feed motor.
III - 5