Epson LQ-2550 Technical Manual page 80

Voltage Regulation
Figure 2-26 shows the + 5 V voltage regulator circuit. The voltage is regulated by shunt regulatorL5431
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by voltage dividing resistors R 13 and R 15. If the output exceeds + 5 V, current IK flows to the cathode
of Q4, the photo diode and photo transistor of PC 1 turns on, Q2 turns on, and Q 1 turns off.
T1
2-26. +5 V Voltage Regulator Circuit
Figure
3
1
Pc 1
2-33
+12
R12