Error Detection Amplifier Circuit; Over Voltage Protection - NEC MultiSync FP1370 Service Manual

8-5. Error Detection Amplifier Circuit

The output voltage +80.2V is compared with the reference voltage at the error amplifier IC671.
An error signal is applied to the control circuit via the photocupler PC621.
CONTROL
CIRCUIT

8-6. Over Voltage Protection

If some failure occurs and the output voltage of the secondary windings of T601 increase, the voltage of the
auxiliary winding of T601 also increase proportionally. When the voltage of C623 and IC621 pin 9 increase.
This action will stop the oscillator with in IC.
R674
PC621
2
IC671
3
(Fig.8-5) Error Detection Amplifier Circuit
IC621
VIN
9
GND
C623
2
(Fig.8-6) Over Voltage Protection
R675
1
C673
D623 D625
+
-
8-45
+80.2V
GND
T601