MAIN/SUB Voltages
The F+15V from the power supply is applied to pins 6, 7, and 8 of connector A6 on the A board. The 15V is
applied to the voltage input pin (pin 9) of the “SUB+5V/SUB+9V” dual regulator IC3500. The 15V is also
used to keep pin 1 and pin 15 high.
Pin 1 and pin 15 are the “ON/OFF” pins. When pin 1 is high, pin 3 outputs 5V. When pin 15 is high, pin 13
outputs 9V.
D3500 monitors the 15V line for “OVER VOLTAGE” condition. If the 15V becomes excessive, D3500
conducts to turn on Q3500. When Q3500 is on, pin1 and pin 15 go low to disable IC3500.
The 9V from pin 13 of IC3500 is applied to the 3.3V DC-DC converter (IC5600) to generate the SUB3.3V.
The 9V is also applied to the 1.2V/1.8V DC-DC converter (IC5601) to generate the SUB1.2V and the
SUB1.8V
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