Epson 440 Service Manual page 57

EPSON Stylus Color 600
The C206 PSB/PSE board has various control circuits to stop output if malfunction on the power supply
board, on the main board or on the duty of printer mechanism happen. Following explains each control and
protection circuits.
1) +42V Line Constant Voltage Control Circuit:
The output level of the +42V line is monitored by a detection circuit consisting of seven Zener diodes.
This circuit prevents voltage from dropping for constant output voltage.
2)+5V Line Over voltage Protection Circuit:
This protection circuit is in the same line as +42V overvoltage protection circuit is located. The output
voltage level of the +5V line is monitored by a Zener diode. This circuit shuts down the circuit operation
forcefully when the voltage level exceeds +9V.
3) +42VDC Line Over voltage Circuit
This ciruit is in the same line as +5V line over voltage protection circuit is located. The output level is
monitored by two Zener diodes. If the voltage level exceeds +48VDC, this circuit stops circuit
operation forcefully.
4) +5V Line Constant Voltage/Constant Current Control Circuit:
The output current is monitored by a +5VDC generation switching control IC(IC51), which also
monitors the output voltage. This information is input to the internal comparator and stabilizes+5V
line. Also, operation of the secondary side switch is explained below.
1) When the power is turned on, Q1 repeats ON/OFF automatically along with the increase and
decrease of energy on the trans coil at the primary side. While the power is being on, PSC
signal is input to the power supply board from the C200 main board.
2) This signal turns Q84 on and it becomes possible to discharge energy between 8-9 of T1.
At this time, even if the power is turned off, the electrolytic capacitor keeps Q84 on for a while.
By this electrolytic capacitor, output is hold at least 30 seconds even after the power is turned off.
This time helps the printer to complete the P-Off operation.
2-20
Figure 2-18. C206 PSB/PSE Board Block Diagram
Rev. A