Xerox WorkCentre C2424DX Service Manual page 57

on a triac to activate a heater, it is turned on for only a fraction of a second. The main
board must constantly readdress each heater it wants to remain on. This means if the
print engine firmware should fail, the heaters automatically shut off.
The printer is also protected by thermal fuses. A thermal fuse opens in the unlikely
event of a "runaway" heater following a hardware failure. The drum and the paper
preheater thermal fuses are located on the paper preheater. Additional thermal fuses
are located on the printhead and on the ink melting elements.
The DC power supply generates + 3.3 V, +/- 15 V, and +/- 50 V. These voltages are
used directly or regulated to other voltage values as needed by various circuits in the
printer. The power control board regulates +/- 15 V to +/- 12 and other voltages. The
main board also has regulators providing + 5 V, + 2.5 V, and + 1.8 V. The power
supply outputs + 3.3 V in ENERGY STAR mode. Fuse F1 provides protection for the
switching power supply in the DC section.
Warning
Theory of Operation
Do not touch the power supply; AC line voltages are present. The
power switch does not disconnect power from the printer. The
power switch signals the supply and the printer logic to begin a
shutdown sequence.
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