Epson EPL-N4000 Service Manual page 91

EPSON EPL-N4000/EPL-N4000+


Low Voltage Power Supply (LVPS)
Takes filtered AC voltage and converts it into regulated +24VDC
and +5VDC.

The LVPS contains overcurrent protection circuits. If an
excessive current begins to flow through any of the components
supplied by the LVPS, the LVPS immediately shuts down all low
voltage output. To reset the LVPS after an overcurrent
shutdown; switch off the printer, wait a few minutes, then switch
on the printer.

The LVPS contains open circuit protection circuits. If the
LVPS detects that a circuit is open for longer than one minute,
the LVPS slowly decreases the LVPS output until the output is
zero. To reset the LVPS after an open circuit shutdown; switch
off the printer, wait a few minutes, then switch on the printer.

The LVPS contains a low +24VDC output protection circuit. If
the LVPS detects the +24VDC output dropping below +15VDC,
the LVPS slowly decreases the +24VDC LVPS output until the
output is zero.
LVPS Fan: A +24VDC fan that cools the LVPS PWB.


Machine Control Unit (MCU PWB)
Takes the +24VDC and +5VDC generated by the LVPS and
distributes them to the various components through out the printer,
including +24VDC to the High Voltage Power Supply (HVPS).

Interlock Switches SW1 and SW2: Used as a safety measure.
The main interlock circuit for this printer is actually two
separated switches wired in series with the MCU PWB. When
the EP Cartridge is in place, Interlock Switch SW1 is closed.
When the Left Front Cover is closed, Interlock Switch SW2 is
closed. With both switches closed, the circuit is complete and
the MCU PWB sends +24VDC to the HVPS and other printer
components.
Rev.B
If either SW1 is open (the EP Cartridge removed) or SW2 is open (the
Left Front Cover is open) the MCU PWB cuts all +24VDC output from
the MCU PWB.
Even though the interlock switches cut the +24VDC
output from the MCU PWB, +24VDC output from the
LVPS is still present throughout the printer as well as
110VAC line voltage along the AC paths in the
printer.


High Voltage Power Supply (HVPS)
Takes the +24VDC received from the MCU PWB and converts it to
the high voltages that are required by the printer xerographic
components.

The HVPS contains overcurrent protection circuits. If an
excessive current begins to flow through any of the xerographic
components, the HVPS immediately shuts down all high voltage
output. To reset the HVPS after an overcurrent shutdown; switch
off the printer, wait a few minutes, then switch on the printer.
Chapter 2 Operating Principles
77