The low-voltage power circuit has protective function against overcurrent and overvoltage. Once there flows an excessive current accidentally to the load side for

some trouble such as a short-circuit problem, or overvoltage occurs, it automatically cuts off the output voltage to prevent failures in the low-voltage power circuit.

In case that no DC voltage is supplied from the low-voltage power circuit, turn off the power switch (SW4) anyway. Do not turn on the power again as far as the

root cause is not found at the load side since the protective function may still work.

There are two fuses, FU3801 and FU3901, in the circuit for other protective function. The fuses blow and cut off the AC power, once AC overcurrent flows into

the AC line.

To recover the low-voltage power circuit in case of functioning the protection, turn the power OFF (by switching off or unplugging) and leave the printer off for 15

seconds or longer, then turn the printer ON again.

11.4.2.2 Safety

For the safety reason for the users and the service technicians, the +24V DC line is intentionally divided into two ways, +24VA and +24VB.

The +24VA is supplied from the DC controller PCB all the time, whereas the power supply of the +24VB stops when the front cover detection switch (SW1) is cut

off.

The high-voltage power PCB and motors are supplied with the +24VB. They stop when the front cover or the reverse assembly cover is opened. This is to protect

the users and the service technicians from an electric shock or injury to their hands.

The +24VB also functions as the front cover detection signal. The CPU determines the front cover or the reverse assembly cover open when the +24VB supply stops.