Sony ICF-C255RC - Auto Time Set Clock Radio User manual

ICF-C255RC
AEP Model SERVICE MANUAL
FM/MW/LW RADIO CONTROLLED CLOCK RADIO
SPECIFICATIONS
Ver 1.0 2000. 05

— 2 —
SECTION 1
GENERAL
This section is extracted
from instruction manual.
1. Check the area of your repair for unsoldered or poorly-soldered
connections. Check the entire board surface for solder splashes
and bridges.
2. Check the interboard wiring to ensure that no wires are
"pinched" or contact high-wattage resistors.
3. Look for unauthorized replacement parts, particularly
transistors, that were installed during a previous repair. Point
them out to the customer and recommend their replacement.
4. Look for parts which, through functioning, show obvious signs
of deterioration. Point them out to the customer and
recommend their replacement.
5. Check the B+ voltage to see it is at the values specified.
6. Flexible Circuit Board Repairing
• Keep the temperature of the soldering iron around 270˚C
during repairing.
• Do not touch the soldering iron on the same conductor of the
circuit board (within 3 times).
• Be careful not to apply force on the conductor when soldering
or unsoldering.
SAFETY CHECK-OUT
After correcting the original service problem, perform the following
safety checks before releasing the set to the customer.

—3 —

—4 —
SECTION 2
DISASSEMBLY
Note : Follow the disassembly procedure in the numerical order given.
•The equipment can be removed using the following procedure.
Key board
Ferrite rod antenna board
Cabinet (upper)Set Main board Power boar
d
2-1. CABINET (UPPER)
S
4 Cabinet (upper)
6 Speaker
2 Two claws
7 Box assy, ANT
connector
8 Box assy, ANT
5 Remove the two solderings.
3
1 Five screws (M3 ×14)
Precaution when attaching
the cabinet (upper).
Align the button (alarm) with
knob of the dial (alarm) assembly
to attach it.

—5 —
2-2. KEY BOARD
1 Two claws
5 Two claws
2 Two claws
6 Chassi
s
4 Key board
3 Connector (CN200)
7 Cabinet (lower)
2-3. MAIN BOARD
8 Main board
6 LED board
3 Alarm dial board
4 Claw
7 Connector (CN150)
5 Connector (CN2)
1 Connector (CN201)
2 Two screws (BTP 2 ×8)

—6 —
2-4. POWER BOARD
7 Power board
2 Terminal
4 Power cord
3 Remove the
two solderings.
5 Remove the
six solderings.
6 Transformer
power
1
2-5. FERRITE ROD ANTENNA BOARD
S
Set the Antenna cord as illustrated below,
then install the antenna box (upper).
4 Box (upper), antenna
2 Two claws
Box (upper), antenna
Box (upper), antenna
3 Box (lower),
antenna
5 Ferrite-rod
antenna board
Ferrite-rod antenna board
Antenna cord
1 Three screws (B1.7 ×8)
Antenna cord setting
(BOX ASSY, ANT)

SECTION 3
ELECTRICAL ADJUSTMENTS
[FM]
Setting:
BAND switch: FM
[MW/LW]
Setting:
BAND switch: MW/LW
Repeat the procedures in each adjustment several times, and the
frequency coverage and tracking adjustments should be finally done
by the trimmer capacitors.
FM TRACKING ADJUSTMENT
Adjust for a maximum reading on level meter.
L3 CT3
87.5 MHz 108 MHz
AM IF ADJUSTMENT
Adjust for a VT VOLTAGE 2.65 ± 0.1V on volt meter.
T1
5450 kHz
MW FREQUENCY COVERAGE ADJUSTMENT
Adjust for a VT VOLTAGE 2.25 ± 0.05V on volt meter.
L1
531 kHz
MW TRACKING ADJUSTMENT
Adjust for a maximum reading on level meter.
L4-1 CT1
621 kHz 1,404 kHz
LW FREQUENCY COVERAGE ADJUSTMENT
Adjust for a maximum reading on level meter.
CT4
153 kHz
LW TRACKING ADJUSTMENT
Adjust for a maximum reading on level meter.
L4-2 CT2
162 kHz 243 kHz
• Adjusting Location: MAIN board (Component Side)
— 7 — — 8 —
T1 AM IF adjustment
FM TRACKING adjustment
L1 MW FREQUENCY COVERAGE
adjustment
CT1 MW TARCKING adjustment
CT3
L3
L4-2 LW TRACKING adjustment
L4-1 MW TRACKING adjustment
CT2 LW TARCKING adjustment
CT4 LW FREQUENCY COVERAGE
adjustment
2-6. POWER CORD AND ANTENNA CORD SETTING
Power board
Main board
Set the power cord and the antenna cord
as illustrated below,
then install the cabinet (lower).
Power cord
Power cord
Antenna cord
Antenna cord
Cabinet (lower)
+
–
FM RF signal generator
22.5 kHz frequency
deviation by 400 Hz
signal FM lead wire antenna terminal
speaker terminal
0.01 µFset
level meter
+
–
AM RF SSG
Put the lead-wire
antenna close to
the set.
30% amplitude
modulation by
400 Hz signal
Output level: as low as possible
set
speaker terminal
level meter

ICF-C255RC
—9 ——10 —
4-1. PRINTED WIRING BOARDS
Note on Printed Wiring Boards:
•X: parts extracted from the component side.
•b: Pattern from the side which enables seeing.
Ref. No. Location
D1 D-9
D5 E-8
D6 E-7
D7 E-6
D8 E-5
D9 E-3
D10 E-3
D100 D-5
D101 D-5
D151 D-4
D152 D-4
D153 D-4
D154 C-4
D155 C-4
D156
IC1 C-8
IC100 E-6
Q1 D-9
Q2 C-7
Q3 B-8
Q4 B-8
Q5 D-8
Q6 E-9
Q7 D-6
Q8 D-6
Q9 E-4
Q10 E-4
Q100 E-5
Q101 E-5
Q151 C-6
•Semiconductor
Location
SECTION 4
DIAGRAMS
KEY BOARD
POWER BOARD
LED BOARD
MAIN BOARD
1-676
-852-
1-676-851- 11
(11)
11
(11)
1-676-850-
11
(11)
1-676-849-
12
(12)
1-674-952- 11
(11)
C30
C9
C19
C24
C10
C16
R16
JC13
R1
R2 C2
C26
C117
R18
R28 R27
JC11
Q4
C25
C108
C156
C157
C158
E
E
E
E
CF1
CF2
CF3
X100
15
28
114
1
1
1
5
4
18
41
32
FERRITE-ROD ANTENNA BOARD
FERRITE
ROD
ANTENNA
BPF1
VR1
FM
ANTENNA
VOL
CT1
CT3
CT4
CT2
C8
T1
L3
L1
L4
AM FERRITE-ROD
ANTENNA
K
E
D5
D100
D155
D154
D152
D153
D101
D151
D6D7D8
D9
D10
Q151
W200
W151
EE
E
E
1
1415
28
29
42 43
56
LCD100 (LIQUID CRYSTAL DISPLAY)
E
CN150
13
CN2
13
W2
14
W150
CN201
E
E
HI
LOW
S1 BRIGHTNESS
H
L
18
CN200
B
A
ALARM
MODE
T150
POWER
TRANSFORMER
P150
AC IN
S213
CLOCK
S210
DST
S209
M5
S208
M4
S204
ON
S202
OFF
S207
M3
S206
M2
S205
M1
S200 S201
S203
BAND
S211
SNOOZE
S212
A-RESET
S214
S215
SP1
(SPEAKER)
12
A
B
C
D
E
F
G
345678910
TO
ALARM
DIAL
16
TIME
TIME
TUNING
D5-D8
BACK LIGHT
JC153
JC119
JC120
JC158
JC144
JC143
JC159
JC160
C120
C120
JC155
JC154
JC156
JC157
R123
R151
C159
R26
R25
R153
R22
R21
R120
R101
R17
CN202
Q1
D1
Q5
JC112
JC161
C459 R456
L451
JC162
JC102
X451
4
2
1
3
20
1110
1
R459
C460 C456
C457
R458
R460
R461
C451
C454
C455
IC451
R453
PS150

ICF-C255RC
—11 ——12 —
4-2. SCHEMATIC DIAGRAM
Note on Schematic Diagram:
•All capacitors are in µF unless otherwise noted. pF: µµF
50 WV or less are not indicated except for electrolytics
and tantalums.
•All resistors are in Ωand 1/4W or less unless otherwise
specified.
•f: internal component.
•C: panel designation.
•U: B+ Line.
•H: adjustment for repair.
•Voltages are dc with respect to ground under no-signal
(detuned) conditions.
no mark : FM
( ) : MW/LW
∗: Impossible to measure
•Voltages are taken with a VOM (Input impedance 10 MΩ).
Voltage variations may be noted due to normal produc-
tion tolerances.
•Signal path.
F: FM
f: MW/LW
The components identified by mark 0or dotted
line with mark 0are critical for safety.
Replace only with part number specified.
•Waveform
2Vp-p
1 IC100 wf (XOUT)
1V/div
14µsec 10µsec/div