Epson FX-2170 Service Manual page 70

FX-2170 Service Manual
7. +5 V Line Constant Voltage Control Circuit
The +5 V line constant voltage control circuit is shown below.
R81
GND
GND
16
Figure 2-29 +5 V Line Constant Voltage Control Circuit
Port 16 of IC51 (TL494CN) monitors the + 5 V line, and the voltage is compared with the standard voltage,
which is input into port 15. When the voltage of port 16 goes below 4.81 V or above 5.17 V, the pulse width
of the PWM signal, which is output from port 8, changes and the +5 V line is kept between 4.81 V to 5.17 V.
Rev.A
+35V
R60
R59
Q51
ZD55
R61
R51
15
-
8
IC51
TL494CN
L51
R 5 3
R88
R64
D51
R 6 5
Operating Principles
+5v Line
G N D
2-21