Appendix D-66 Product Overview Rev. A
Confidential
Input Circuit
Logic Power Source Circuit
The logic power source circuit generates the power for this printer. The CPU, GA, and most
other circuits do not operate if voltage is not output by the logic power source circuit. The
power source circuit has an input of 24V, and uses a dedicated DC/DC converter IC (U11:
PQ1CZ1) to output 5V ± 4%.
Figure D-65
The output voltage is determined by the potential division of R82 and R85. In other words, the
circuit operates so that the crossover voltage of R82 and R85 is 1.26 V.
The input voltage of 24V for the power supply circuit is supplied to U11 through the R2 fuse
resistor (KOA RF73B2HTE0.51). R3 may burn out in the event of a malfunction in the U11 area.
R3 will also burn out in the event of excessive VCC voltage (Approx. 7.5 V or more). This fuse
resistor cannot be replaced. Therefore, the circuit cannot be repaired by replacing the R3 in the
event it has burned out due to a circuit malfunction.
TableD-14 Power source specifications
Item Min. Typ. Max. Remarks
Output Voltage (V) 4.85 5.04 5.24
Output Current (A) 1 - -
Input Voltage (V) 21.6 24 26.4
Over-Current
Protection (A)
1.55 2 2.6 L2, D13, C35 not provided. The peak current
is detected, and detected voltage is
lowered. Automatic reset.
Over-Voltage
Protection (V)
7.5 CY1 goes On after detection, and R3 burns
out. Does not reset.
VCC
AVCC
24VB
R253
C35
C38
R3
U11
PQ1CZ1
VIN
1
VOUT
2
COM
3
ADJ
4
ON/OFF
5
G
6
L2
D13
C37
CY1
ZD3
L1
R82
C155
R85
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