Ricoh SP C440dn, Field Service Manual, Page: 87 / 654

4. Replacement and Adjustment
Notes on the Main Power Switch
Push Switch
The main power button of this machine has been changed to a push-button switch (push button) from the
conventional rocker switch. The push switch has characteristics and specifications different from the
rocker switch. Care must be taken when replacing and adjusting parts.
Characteristics of the Push Switch (DC Switch)
Power is supplied to the machine even when the main power switch is turned OFF.
The push switch in this machine uses DC (direct current). Therefore, if the AC power cord is
connected to an electrical outlet, power is supplied to the controller board, the operation unit and
other modules even when the main power is turned OFF. When replacing the controller board and
the operation unit in this state, not only these boards, it will damage other electrical components.
In 100V models, only one of the AC lines for the fusing unit is shut off when you turn off the main
power; the other line carries current even when you turn off the main power switch.
So, when performing maintenance work such as replacing parts, in addition to turning off the main
power with the push switch, always unplug the AC power cord.
When you disconnect the power cord from the AC wall outlet, inside the machine there is still
residual charge.
When you disconnect the power cord from the AC wall outlet, inside the machine for a while there
is still residual charge. Therefore, if you remove boards in this state, it can cause a blown fuse or
memory failure.
• How to remove the residual charge inside the machine
After you unplug the power cord from the AC wall outlet, in order to remove the residual
charge from inside the machine, be sure to press the main power switch. Thus, the charge
remaining in the machine is released, and it is possible to remove boards.
When you reconnect the AC power cord into an AC wall outlet, the machine will start
automatically.
In order to remove the residual charge, push the main power switch while you disconnect the AC
power cord. At that time, the power ON flag inside the machine is set. Therefore, after you finish
work on the machine and reconnect the power cord to the AC, even if you do not press the main
power switch, the machine will start automatically and the moving parts will begin to move. When
working on moving parts, be careful that fingers or clothes do not get caught.
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