Service manual
UX-22oocMu/cMC
I0215oCMUCMc
[4] Circuit description of power supply PWB
1. Block diagram
TRANSFORMER
SWITCHING 1
1
Fl
4.OA 125V
ACIN 0
w RECTITYING
+5v
12ov 0
50/6OHZ
GND
+24V
_ CIRCUIT
- +24V
A
The power unit intakes input of AC 12OV, 50/60 Hz and supplies output
of +24V, +7.4V and +5V as shown in the block diagram. (See Fig. 8.)
2-1. Filter, rectifying and smoothening circuit
In the filter section, the noise generated from the power unit is elimi-
nated from being discharged to the external, and external noise is pre-
vented from entering. Thunder or other excessive surge is prevented by
the varistor 21.
In the rectifying and smoothening section, AC input is rectified by the
diodes Dl 0, 11, 12 and 13, and is smoothened by the capacitor C5.
Thus, DC voltage is supplied to the switching section. Moreover, the
thermistor NTCl prevents surge current when the power is turned on.
2-2. Switching section
The circuit uses the tinging choke converter of a self-excited type.
Since MOS.
FETQl is repeatedly turned on and off in this system, the DC voltage
supplied from the rectifying and smoothening section is converted into
the high frequency pulses. While Ql is on, energy is accumulated in the
primary winding of the transformer Tl , and while Ql is off, energy is
discharged to the secondary side. Thus, the power is supplied.
Moreover, the frequency is varied depending on the load of the output.
As the load becomes the heavier, the frequency becomes the smaller to
extend the ON period.
The constant voltage is controlled by applying the feedback to the con-
[5] Circuit description of CIS PWB
The CIS board picks up optical information from the document, con-
verts it into an electrical (analog) signal and transfers it to the control
board.
(1) Block diagram
SH
CISCLK
VLED
GLED
CIS
+5v
GND
AiN
Fig. 9
Fig. 8
COUPLER u
trol circuit through the photo coupler PC1 from +24V output. The
overcurrent-protective circuit detects that the ON period becomes the
wider as the output load becomes the heavier. For the control, the OFF
period is extended by the control circuit to squeeze the energy which is
accumulated in the primary winding of the transformer Tl.
For protection against overvoltage, the rise of the output voltage of +24V
on the secondary side is brought into the overcurrent state through the
continuity of the power zener diode D104 between +24V output and
GND. Thus, the overcurrent-protective circuit of the control circuit is ac-
tivated for the protection.
2-3. +24V circuit
Output is supplied by rectifying and smoothening the output of the trans-
former Tl with the diode Dl 01 and capacitor Cl01 .
2-4. +5V circuit
+5 V output is generated by rectifying and smoothening the output of the
transformer Tl with the diode D102 and capacitor Cl02 and stabilizing
it with the 3-terminal regulator IC103.
2-5. +7.4V circuit
This circuit rectificats and smoothings the high-frequency pulse voltage,
and output the DC +7.4V to the equipment.
(2) Description of blocks
1. CIS
The DLlOO-05AUJS is a highly sensitive charged coupled image sensor
that consists of 2160 picture elements.
Receiving four drive signal (SI,CLK) from the control board, the tranfened
photoelectric analog signal SIG is impedance converted, and the signal
AiN, is supplied to the control board.
2. Waveforms
1. CLK, SI, SIG signals within the control board.
CLK JJ-/JJ_.______JJ-L
s, n_______ n
SIG U .------ A
Fig. 10
5-14