Overcurrent/overvoltage protection
The low-voltage power supply has a protective circuit against overcurrent and overvoltage to prevent
failures in the power supply circuit. The low-voltage power supply automatically stops supplying the DC
voltage whenever excessive current flows or voltage abnormally increases.
If the dc voltage is not being supplied from the low-voltage power supply, the protective function may be
running. In this case, turn off the power switch and unplug the power cord. Do not turn the power switch on
until the root cause is found.
The LVPS has two fuses on the PCA. The LVPS 24V output is interrupted to the fuser and the high-voltage
power supply if the either of the interlock switches (SW3 and SW4) is in the off position (door open).
WARNING! The product power switch only interrupts dc voltage from the LVPS. The AC voltage is present in
the product when the power cord is plugged into a power receptacle and the power switch is in the off
position. You must unplug the product power cord before servicing the product.
WARNING! If you believe the overcurrent or overvoltage protection circuits have been activated, do not
plug in the product power cord or turn on the product power until the cause of the failure is found and
corrected.
In addition, fuses in the low-voltage power supply protect against overcurrent. If overcurrent flows into the
AC line, the fuses melt and cut off the power distribution.
20 Chapter 1 Theory of operation ENWW
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