Sony Dream Machine ICF-C795RC User manual

MICROFILM
SERVICE MANUAL
FM/AM RADIO CONTROLLED CLOCK RADIO
AEP Model
SPECIFICATIONS
ICF-C795RC
Ver 1.0 1999. 08

– 2 –
TABLE OF CONTENTS
1. GENERAL ................................................................... 3
2. DISASSEMBLY ......................................................... 5
3. ELECTRICAL ADJUSTMENTS......................... 7
4. DIAGRAMS
4-1. Block Diagram ................................................................ 9
4-2. Schematic Diagram ......................................................... 13
4-3. Printed Wiring Boards .................................................... 15
4-4. IC Pin Function Description ........................................... 18
5. EXPLODED VIEWS................................................ 19
6. ELECTRICAL PARTS LIST ............................... 21
Notes on chip component replacement
• Never reuse a disconnected chip component.
• Notice that the minus side of a tantalum capacitor may be dam-
aged by heat.
SAFETY-RELATED COMPONENT WARNING!!
COMPONENTS IDENTIFIED BY MARK !OR DOTTED
LINE WITH MARK !ON THE SCHEMATIC DIAGRAMS
AND IN THE PARTS LIST ARE CRITICAL TO SAFE
OPERATION. REPLACE THESE COMPONENTS WITH
SONY PARTS WHOSE PART NUMBERS APPEAR AS
SHOWN IN THIS MANUAL OR IN SUPPLEMENTS PUB-
LISHED BY SONY.
CF
2
CF3
mark
Mark Center frequency
red 10.70 MHz
blue 10.67 MHz
orange 10.73 MHz
black 10.64 MHz
white 10.76 MHz
HOW TO CHANGED THE CERAMIC FILTERS
This model is used two ceramic filters of CF2 and CF3.
You must use same type of color marked ceramic filters in order
to meet same specifications.
Therefore, the ceramic filter must be changed two pieces together
since it’s supply two pieces in one package as a spare parts.

– 3 –
SECTION 1
GENERAL This section is extracted from
instruction manual.

– 4 –

– 5 –
CHASSIS ASSY
Note: Follow the disassembly procedure in the numerical order given.
SECTION 2
DISASSEMBLY
2 claw
2 three claws
1 screw (P3 × 14)
1 four screws (P3 × 14)
3 rear cabinet
4 connector
(CN301)
7 chassis assy
5 Break the soldering of
speaker lead.
6 button (DST)
6 knob (brightness)
POWER CORD SETTING
Set the power cord as illustrated below,
then install the cabinet.
rear cabine
t
power cord
boss
rear cabinet
power cord
Put the secondary flat cable
between bosses to fix.

– 6 –
BOX (UPPER) , ANTENNA
ANTENNA CORD SETTING
2 claw
2 claw
3 box (upper), antenna
1 three screws
Set the antenna cord as illustrated below,
then install the antenna box.
box (lower), antenna
coil leadantenna cord
antenna, ferrite-ro
d

– 7 –
SECTION 3
ELECTRICAL ADJUSTMENTS
0 dB = 1 µV
[AM]
Setting:
Band switch: AM
[FM]
Setting:
Band switch: FM
• Repeat the procedures in each adjustment several times, and
the tracking adjustments should be finally done by the trimmer
capacitors.
• Remove FM antenna in FM adjustments.
Adjustment Location: MAIN board (See page 8)
AM RF signal
generator
30% amplitude
modulation by
400 Hz signal
Output level: as low as possible
Put the lead-wire
antenna close to
the set.
+
–
level meter
set
8 Ω
MAIN board TP (SP GND)
MAIN board
TP (SP +)
FM RF signal
generator
22.5 kHz frequency
deviation by 400 Hz
signal
Output level: as low as possible
+
–
level meter
MAIN board TP (SP GND)
MAIN board
TP (SP +)
set
MAIN board
TP (FM-IN) 8
Ω
0.01 µ F
MAIN board
TP (FM GND)
digital voltmeter
100 k Ω
TP (VT)
TP (FM GND) +
–
MAIN board
AM IF ADJUSTMENT
Adjust for a maximum reading on level meter.
T1 450 kHz
AM VCO VOLTAGE ADJUSTMENT
Adjustment Part Frequency Display Reading on Digital Voltmeter
L5 531 kHz 2.65 V ± 0.1V
Confirmation 1,602 kHz Less than 9.5 V
AM TRACKING ADJUSTMENT
Adjust for a maximum reading on level meter.
L1 621 kHz
TC1 1,404 kHz
FM VCO VOLTAGE ADJUSTMENT
Adjustment Part Frequency Display Reading on Digital Voltmeter
L4 87.5 MHz 3 V ± 0.1 V
Confirmation 108 MHz Less than 11.8 V
FM TRACKING ADJUSTMENT
Adjust for a maximum reading on level meter.
L3 87.5 MHz
TC3 108 MHz

– 8 –
Adjustment Location:
L1
AM Tracking Adjustment
L3 TC3
FM Tracking Adjustment
T1
AM IF Adjustment TC1 AM Tracking Adjustment
L4 FM VCO Voltage Adjustment
L5 AM VCO Voltage Adjustment
TP (VT) TP (SP+)
TP (SP GND)
TP (FM-IN)
TP (FM GND)
– MAIN BOARD (Component Side) – – MAIN BOARD (Conductor Side) –
ANTENNA SECTION
Antenna Adjustment
Setting:
Procedure:
1. Set a SSG.
2. Connect an oscilloscope to TP451 and TP452 on the AN-
TENNA board.
3. Adjust L451 on the ANTENNA board for a maximum wave-
form level on the oscilloscope.
Adjustment Location:
TP452
TP451 L451
Antenna
Adjustment
– ANTENNA BOARD (Conductor Side) –
SSG
Frequency:
77.5 kHz
Modulation:
no modulation
antenna
unit
loop antenna
ANTENNA board
TP451
ANTENNA board
TP452
+
–
oscilloscope
(DC range)
Probe: 10:1,
10 M
Ω

ICF-C795RC
– 9 – – 10 – – 11 –
4-1. BLOCK DIAGRAM
SECTION 4
DIAGRAMS
12
9
14 17
10
5 7
FM
FRONT-END
AGC
AMPLIFIER
ANTENNA
RECTIFIER &
INTEGRATOR DECODER
FM
IF AMP
AF
POWER AMP
AM IF AMP,
AGC, DET
AM
FRONT-END 16
19
FM RF
IN
FM/AM
FE OUT
CF2
10.7MHz
CF1
450kHz
CF3
10.7MHz
FM
RF
FM
IF IN
2
FM
DISCRIMINATOR
TUNING METER
FM
DISCRI
27
AF
OUT SP301
(SPEAKER)
AF
IN
23 24
DET
OUT
AM
IF IN
METER
NF VOL
15
1
2
3 4
FM/AM
BAND
SELECT
AM OSC
L5
AM OSC L4
FM OSC
X50
75kHz
X451
77.5kHz
L1
AM FERRITE-ROD
ANTENNA
L451
FERRITE-ROD
ANTENNA
L451
ANT1
FM LEAD
ANTENNA
FM OSC
AM RF
IN
L3
FM RF
FM/AM FRONT-END,
FM/AM IF AMP, DET, AGC, AF AMP
IC1
FM/AM PLL
IC50
TIME CODE RECEIVER
IC451
SYSTEM CONTROLLER,
LCD DRIVER, KEY CONTROL
IC100
TC1 D4-1
B+
TC3
VR1
VOL
+
+
L4
FM VCO VOLTAGE
D74
A RADIO
D75
B BUZZER
S50
BRIGHTNESS
(LCD BACK LIGHT)
D70 – 73
(LCD BACK LIGHT)
D74 D75 –2
–1
L5
AM VCO VOLTAGE
L1, TC1
AM TRACKING
L3, TC3
FM TRACKING
T1
AM IF
B.P.F.
BPF1
LOW-PASS FILTER
Q50, 51
LED DRIVE
Q53, 54
MUTING
Q4
• SIGNAL PATH
: FM
: AM
05
D2
D3
AC IN
BACKUP B+
(SYSTEM CONTROLLER IC100 B+)
B+
BZ-CTRL
35
ALM A
6
ALM B
7
BUZZER
36
DATA
DATA IN
DA
PD1
27
5
15
CLK CK
26
4
CE CE
34
3
MUTE
PDET
33
28
RESET
18
AM IN
11
FM IN
XOUT
XIN
22 23
X101
4.19MHz
X1 X2
19 20
X100
32.768kHz
XT1
1
BIAS
2
VLC0
3
VLC1
4
VLC2 XT2 S0 – S23
12
P1
8
D100
D101
VT B+
RECT
D351 – 354
REGULATOR
Q57
T301
POWER
TRANSFORMER
RECT
D355
RESET SIGNAL
GENERATOR
IC101
COM0 – COM3
S101, 201 – 218
(KEY MATRIX)
60 – 37 61 – 64
KS0 – KS4
10 – 13, 8
KR0 – KR3
14 – 17
LIQUID CRYSTAL DISPLAY
LCD100
LCD REFERENCE
VOLTAGE GENERATOR
IC102
D4-2
D102
D60, 61
HIGH
LOW
REC DEC
INT
RF
IN
Q2A Q2B
Q1A Q1B
25
13 14
FLA FLB
10 11
5 6
7TCO 169
8
2
MAIN KEY board
MAIN board
TRANSFORMER board
ANTENNA board
ALARM KEY board
• Circuit Boards Location

ICF-C795RC
– 12 – – 13 – – 14 –
4-2. SCHEMATIC DIAGRAM • See page 17 for IC Block Diagrams.
• Waveforms
– MAIN board –
1IC50 2(XIN)
500 mV/DIV, 5 µs/DIV
3IC100 ws (X1) (*1)
1 V/DIV, 100 ns/DIV
2IC100 ql (XT1)
1 V/DIV, 10 µs/DIV
*1)
Oscillation will be given out for 250 ms with following conditions.
•Turn the radio on.
•Change the band.
•Change the tuning (manual or preset).
1.8 Vp-p
13.3 µ s
2 Vp-p
30.5 µ s
240 ns
2.7 Vp-p
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 and waveforms are dc with respect to ground
under no-signal (detuned) conditions.
no mark : FM
():AM
• Voltagesare taken with aVOM (Input impedance 10MΩ).
Voltage variations may be noted due to normal produc-
tion tolerances.
• Waveforms are taken with a oscilloscope.
Voltage variations may be noted due to normal produc-
tion tolerances.
• Circled numbers refer to waveforms.
• Signal path.
F: FM
f: AM
Note: The components identified by mark 0or dotted line
with mark 0are critical for safety.
Replace only with part number specified.