Overcurrent/overvoltage protection
If a short-circuit or other problem on the load side causes an excessive current flow or generates
abnormal voltage, the overcurrent/overvoltage protection systems automatically cut off the output
voltage to protect the power supply circuit.
If the overcurrent or overvoltage protection system are activated and the power supply circuit does
not generate dc voltage, it is necessary to turn the power off, correct the problem, and then turn the
MFP on again.
The circuit has two fuses (FU1, FU2), which break and cut off the output voltage if overcurrent flows
through the ac line.
Toner detection
To monitor the toner level, the MFP uses two plate antennas and a toner-level circuit in the high-
voltage power supply circuit. The dc controller PCA detects the toner level and monitors the output
signal of the toner-level circuit. The signal is fed back to the dc controller PCA from the antennas
during the wait and standby operating periods. The dc controller PCA detects toner level from 1% to
100%. If the dc controller PCA detects a low toner level, a message appears on the control-panel
display (see
Resolving control-panel messages).
Cartridge detection
The dc controller PCA detects the presence of the cartridge by using information stored in plate
antenna 2 and the print cartridge memory tag. The dc controller PCA detects the presence (or lack)
of the print cartridge during the wait operating period.
94 5 Theory of operation
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