Xerox Nuvera 100, Service Manual

Page: 59 / 304

General Information 1-59
Power Supply
The power supply has two main, yet interrelated sections: the AC
section and the DC section. In the AC section, power is routed to 14
opto-isolated triacs which, under main board logic control, supply AC
power to the 14 heaters in the printer.
Two fuses provide current protection to the triacs. Fuse F2 and F3
protect the power supply from, most often, a shorted triac caused by a
defective heater. If F2 or F3 fuse blows, it is best to replace the power
supply (and, of course, the defective heater), rather than the fuse.
Otherwise, with the fuse replaced, but the triac shorted, AC power
may be applied to the heater without the printer even being turned
on. Each time the main board turns 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. By this
means, if the print engine firmware should fail, the heaters
automatically shut off. The printer is also protected by thermal fuses
located inside: two fuses for the drum heater, and one each for the
paper preheater and the cap/wipe/purge assembly. A thermal fuse
opens in the unlikely event of a “runaway” heater following a
firmware failure.
The DC power supply gen5 volts for the printer’s logic, + 40
volts for the motors, +54 volts and -52 volts for the printhead drivers,
and
±
12 volts for fans. Fuse F1 provides protection for the switching
power supply in the DC section. The block diagram for the power
supply is illustrated in Figure 1-26.
WARNING
Do not touch the power supply; AC line voltages are present. The
power-switch does not interrupt AC power to the power supply, it
only signals the supply and the printer logic to begin a shutdown
sequence. Even with the power switch in the OFF position, AC line
voltages are present on the power supply, heaters and heater
wiring.
There are no field adjustments necessary on the power supply.