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.

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

claw

three claws

screw (P3

14)

four screws (P3

14)

rear cabinet

connector

(CN301)

chassis assy

Break the soldering of

speaker lead.

button (DST)

knob (brightness)

POWER CORD SETTING

Set the power cord as illustrated below,

then install the cabinet.

rear cabine

power cord

boss

rear cabinet

power cord

Put the secondary flat cable

between bosses to fix.

– 6 –

BOX (UPPER) , ANTENNA

ANTENNA CORD SETTING

claw

box (upper), antenna

three screws

Set the antenna cord as illustrated below,

then install the antenna box.

box (lower), antenna

coil leadantenna cord

antenna, ferrite-ro

– 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

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

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:

AM Tracking Adjustment

L3 TC3

FM Tracking Adjustment

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

14 17

5 7

FRONT-END

AGC

AMPLIFIER

ANTENNA

RECTIFIER &

INTEGRATOR DECODER

IF AMP

POWER AMP

AM IF AMP,

AGC, DET

FRONT-END 16

FM RF

FM/AM

FE OUT

CF2

10.7MHz

CF1

450kHz

CF3

10.7MHz

IF IN

DISCRIMINATOR

TUNING METER

DISCRI

OUT SP301

(SPEAKER)

23 24

DET

OUT

IF IN

METER

VOL

3 4

FM/AM

BAND

SELECT

AM OSC

AM OSC L4

FM OSC

X50

75kHz

X451

77.5kHz

AM FERRITE-ROD

ANTENNA

L451

FERRITE-ROD

ANTENNA

L451

ANT1

FM LEAD

ANTENNA

FM OSC

AM RF

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

FM VCO VOLTAGE

D74

A RADIO

D75

B BUZZER

S50

BRIGHTNESS

(LCD BACK LIGHT)

D70 – 73

(LCD BACK LIGHT)

D74 D75 –2

–1

AM VCO VOLTAGE

L1, TC1

AM TRACKING

L3, TC3

FM TRACKING

AM IF

B.P.F.

BPF1

LOW-PASS FILTER

Q50, 51

LED DRIVE

Q53, 54

MUTING

• SIGNAL PATH

: FM

: AM

AC IN

BACKUP B+

(SYSTEM CONTROLLER IC100 B+)

B+

BZ-CTRL

ALM A

ALM B

BUZZER

DATA

DATA IN

PD1

CLK CK

CE CE

MUTE

PDET

RESET

AM IN

FM IN

XOUT

XIN

22 23

X101

4.19MHz

19 20

X100

32.768kHz

XT1

BIAS

VLC0

VLC1

VLC2

XT2

S0 – S23

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

Q2A

Q2B

Q1A

Q1B

13 14

FLA

FLB

10 11

5 6

7TCO 169

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

2 Vp-p

30.5

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.

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