HP 3380 Service Manual - Page 99
High-voltage power supply circuit, Low-voltage power distribution
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This circuit also controls the image density by changing the primary ac voltage and the developing ac bias according to the print-density setting. Figure 4-7. High-voltage power supply circuit shows the high-voltage power supply circuit. Figure 4-7. High-voltage power supply circuit Low-voltage power distribution The low-voltage power supply circuit converts ac power into +24 Vdc, +5 Vdc, and +3.3 Vdc as required by the printer. The +24 Vdc is divided into +24 V, which is supplied constantly from the low-voltage power supply circuit, and +24 U, which is supplied to the high-voltage power supply circuit and which acts as the door-open detection. When the top cover is open, the door-open switch (SW301) cuts the +24 U to the high-voltage power supply circuit. The circuit contains a fuse for overvoltage protection. FU101 breaks and cuts power if overcurrent flows through the power cord. FU102 (on 110-127 V models) breaks at a lower amperage, as required for lower-voltage units. In addition, the +24 Vdc and +3.3 Vdc power circuitry contains an overcurrent protection circuit that automatically shuts off dc voltage output to prevent power-supply failures if current flow is excessive or voltage generation is abnormal. The circuit automatically resets itself when the printer is turned off. ENWW Printer functions and operation 83