Sony XR-2750 User manual

MICROFILM
XR-2750/2753
AEP Model
UK Model
XR-2750
East European Model
XR-2753
SERVICE MANUAL
FM/MW/LW CASSETTE CAR STEREO
SPECIFICATIONS
Photo: XR-2753
Cassette player section
Tape track 4-track 2-chanel stereo
Wow and flutter 0.08% (WRMS)
Frequency response 30 – 20,000 Hz
Signal-to-noise ratio 58 dB
Tuner section
FM *
Tuning range XR-2750:
87.5 – 108.0 MHz
XR-2753:
65.0 – 74.0 MHz (at 30 kHz step)
87.5 – 108.0 MHz (at 50 kHz step)
Antenna terminal External antenna connector
Intermediate frequency 10.7 MHz
Usable sensitivity 8 dBf
Selectivity 75 dB at 400 kHz
Signal-to-noise ratio 65 dB (stereo),
68 dB (mono)
Harmonic distortion at 1 kHz
0.5% (stereo),
0.3% (mono)
Separation 35 dB at 1 kHz
Frequency response 30 – 15,000 Hz
Capture ratio 2 dB
* There are the numerical values measured at 87.5 – 108.0 MHz
MW/LW
Tuning range MW: 531 – 1,602 kHz
LW : 153 – 281 kHz
Antenna terminal External antenna connector
Intermediate frequency 10.71 MHz/450 kHz
Sensitivity MW: 30 µV
LW: 50 µV
Power amplifier section
Outputs Speaker outputs (sure seal connectors)
Speaker impedance 4 – 8 ohms
Maximum power output 35 W ×4 (at 4 ohms)
General
Outputs Power antenna control lead
Tone controls Bass ±8 dB at 100 Hz
Treble ±8 dB at 10 kHz
Power requirements 12 V DC car battery (negative ground)
Dimensions Approx. 188 ×58 ×183 mm (w/h/d)
Mounting dimensions Approx. 182 ×53 ×164 mm (w/h/d)
Mass Approx. 1.6 kg
Supplied accessories Parts for installation and connections (1 set)
Design and specifications are subject to change without notice.
Model Name Using Similar Mechanism XR-3750/C553SP
Tape Transport Mechanism Type MG-52A-135

– 2 –
TABLE OF CONTENTS
1. GENERAL
Location of Controls ........................................................ 3
Installation ....................................................................... 4
Connections ..................................................................... 5
2. DISASSEMBLY.......................................................... 8
3. ASSEMBLY OF MECHANISM DECK ........... 11
4. MECHANICAL ADJUSTMENTS ....................... 17
5. ELECTRICAL ADJUSTMENTS
Test Mode ........................................................................ 17
Tape Deck Section ........................................................... 18
Tuner Section ................................................................... 18
6. DIAGRAMS
6-1. IC Pin Function Description ............................................ 21
6-2. Printed Wiring Boards –MAIN Section– ........................ 23
6-3. Schematic Diagram –MAIN Section–............................ 27
6-4. Printed Wiring Board –CONTROL Section– ................. 32
6-5. Schematic Diagram –CONTROL Section–.................... 34
7. EXPLODED VIEWS ................................................ 39
8. ELECTRICAL PARTS LIST................................ 43
SERVICING NOTES
Flexible Circuit Board Repairing
•Keep the temperature of the soldering iron around 270 ˚C dur-
ing 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
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.
CAUTION
Danger of explosion if battery is incorrectly replaced.
Replace only with the same or equivalent type recommended by
the manufacturer.
Discard used batteries according to the manufacturer’s instructions.
ADVARSEL!
Lithiumbatteri-Eksplosionsfare ved fejlagtig håndtering.
Udskiftning må kun ske med batteri
af samme fabrikat og type.
Levér det brugte batteri tilbage til leverandøren.
ADVARSEL
Eksplosjonsfare ved feilaktig skifte av batteri.
Benytt samme batteritype eller en tilsvarende type
anbefalt av apparatfabrikanten.
Brukte batterier kasseres i henhold til fabrikantens
instruksjoner.
VARNING
Explosionsfara vid felaktigt batteribyte.
Använd samma batterityp eller en likvärdig typ som
rekommenderas av apparattillverkaren.
Kassera använt batteri enligt gällande föreskrifter.
VAROITUS
Paristo voi räjähtää, jos se on virheellisesti asennettu.
Vaihda paristo ainoastaan laitevalmistajan suosittelemaan tyyppiin.
Hävitä käytetty paristo valmistajan ohjeiden mukaisesti.

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

– 4 –

– 5 –

– 6 –

– 7 –

– 8 –
Note: Follow the disassembly procedure in the numerical order given.
COVER
SECTION 2
DISASSEMBLY
COLLAR (A), HANDLE ASS’Y
1 two screws
(PTT2.6 × 6)
3 Remove the cover to
ward direction A .
2
A
3 screw
(PTT2.6 × 6)
3 screw
(PTT2.6 × 6)
1 seven claws
4 handle ass’y
2 coller (A)

– 9 –
FRONT PANEL ASS’Y
1 two claws
2 front panel ass’y
1 three claws
5 mechanism deck
3 two screws
(PTT2.6 × 6)
2 flexible board
(CNP301)
MECHANISM DECK
1 connector
(CNP331)
4 front chassis
3 three screws
(PTT2.6 × 6)

– 10 –
POWER BOARD
2 two connectors
(CNJ400, 401)
3 power board
1 three screws
(PTT2.6 × 8)
1 two ground point
screws
4 antenna cable
2 ground point
screw
3 main board
MAIN BOARD

– 11 –
SECTION 3
ASSEMBLY OF MECHANISM DECK
Note: Follow the assembly procedure in the numerical order given.
ALIGNMENT OF FRONT SWITCH
1 Align ¢ mark on the rotary switch
the position shown in the figure.
chassis (S) ass’y
2 Align hole in the gear (LDG-D) with the
position shown in the figure.
hole
2 Install the gear (LDG-E).
1 Align hole as shown in the figure.
GEAR (LDGE)

– 12 –
CHASSIS (S) ASS’Y
LEVER (MODE)
2 screw (PS2 × 4)
1 chassis (S) ass’y
2 screw (PS2 × 4)
1. Align ¢ mark on the rotary switch with
hole in the lever (mode).
2. Fit on positions A , B and C and install
the lever (mode).
hole in lever (mode)
¢ mark on rotary switch
lever (mode)
rotary switch
A
B
C

– 13 –
LEVER (PINCH SELECTION)
HEAD PLATE ASS’Y
5 step screw (HP)
5 step screw (HP)
2 Fit shaft in groove.
ATS lever
1 Fit in groove.
3 Press the ATS lever.
4 Position the head plate sub
ass’y as shown in the figure.
groove
1 Align.
2 lever (pich selection)

– 14 –
LEVER (PINCH) ASS’Y
HOUSING
2 Install the hanger on to
two claws of the housing.
1 Install the catch to the hanger.
7 Holder the hanger by bending the claw.
A part
B part
C part
D part
8 Holder the hanger by
bending the claw.
3 Put the housing
under A part.
6 Fit projections on D part.
5 Fit projections on C part.
hanger
4 Fit claw on B part.
1 Fit shaft of the lever (Pinch) ass’y
in hole on the chassis (M) ass’y and
install the lever (pinch) ass’y.
2 two polyethylene washers
shaft
shaft
B
C
C
B
shaft A
3 Install the spring
(pinch press) to shaft A .
Set the ends of spring to B and C .

– 15 –
1 Fit the lever (LDG-A)
on shaft A – C and install it.
shaft A
shaft B
shaft C
3 two type-E stop ring 2.0
2 Fit the lever (LDG-B)
on shafts A and B and
install.
shaft A
shaft B
LEVER (LDG-A) / (LDG-B)
ARM (SUCTION)
2 Move the arm (suction) in the arrow
direction and fit on projection.
1 Fit the arm (suction) on the shaft.
projection

– 16 –
GEAR (LDG-FT)
2 guide (C)
1 three claws
4 Align hole in the gear (LDG-D) with
¢ mark on the lever (LDG-A).
hole
gear (LDG-D)
gear (LDG-A)
3 Move the lever (LDG-B)
in the arrow direction.
1 gear (LDG-A)
2 tension spring (lever LDG)
5 gear (LDG-FT)
6 polyethylene washer
GUIDE (C)
gear (LDG-FB)

– 17 –
SECTION 5
ELECTRICAL ADJUSTMENTS
TEST MODE
This set have the test mode function. In the test mode, FM Auto
Scan/Stop Level and MW Auto Scan/Stop Level adjustments can
be performed easier than it in ordinary procedure.
<Set the Test Mode>
1. Set the “OFF” mode.
2. Push the preset 4 button.
3. Push the preset 5 button.
4. Press the preset 1 button for more than two seconds.
5. Then the display indicates all lights, the test mode is set.
<Release the Test mode>
1. Push the “OFF” button.
SECTION 4
MECHANICAL ADJUSTMENTS
1. Clean the following parts with a denatured-alcohol-moistened
swab: playback head pinch roller
rubber belt capstan
idler
2. Demagnetize the playback head with a head demagnetizer.
3. Do not use a magnetized screwdriver for the adjustments.
4. The adjustments should be performed with the power supply
voltage (14.4V) unless otherwise noted.
•Torque Measurement
Mode Torqu Meter Meter Reading
Forward CQ-403A more than 60 g
Reverse CQ-403R (more than 2.12 oz)
•Tape Tension Measurement
Mode Torqu Meter Meter Reading
Forward CQ-102C 35–65 g•cm
(0.49–0.90 oz•inch)
Forward CQ-102C 0.5–5.0 g•cm
Back Tension (0.01–0.07 oz•inch)
Reverse CQ-102RC 35–65 g•cm
(0.49–0.90 oz•inch)
Reverse CQ-102RC 0.5–5.0 g•cm
Back Tension (0.01–0.07 oz•inch)
FF, REW CQ-201B 60–200 g•cm
(0.83–2.78 oz•inch)

– 18 –
set
FM RF signal
generator
antenna jack
0.01 µF
Carrier frequency : 98.0 MHz
Output level : 20 dB (10.0 µV)
Mode : mono
Modulation : 1 kHz, 22.5 kHz deviation (30%)
test tape
WS-48A
(3 kHz, 0 dB) 4
Ω
set +–
speed checker
or
frequency counte
r
TUNER SECTION 0 dB=1 µV
Cautions during repair
When the tuner unit is defective, replace it by a new one be-
cause its internal block is difficult to repair.
FM Auto Scan/Stop Level Adjustment
Setting:
SOURCE button: FM
See the adjustment location from on page 20 for the
adjustment.
0 dB=0.775VTAPE DECK SECTION
Tape Speed Adjustment
Procedure:
1. Put the set into the FWD PB mode.
Speed checker Frequency counter
–1.5 to +2.5% 2,955 to 3,075 Hz
Specification: Constant speed
Adjustment Location: See page 20.
Procedure:
1. Set to the test mode. (See page 17.)
2. Push the SOURCE button and set to FM.
Display
3. Push the preset 3 button.
Display
4. Adjust with the volume RV2 on TU1 so that the “FM” indica-
tion turns to “FMI” indication on the display window.
But, in case of already indicated “FMI”, turn the RV2 so that
put out light “I” indication and adjustment.
Display
Adjustment Location: See page 20.
FM
98.0

SHUF1
FM
98.0

3
SHUF1
SPEAKER OUT
FM
98.0
3
SHUF1

– 19 –
AM RF signal
generator
set
30 Ω
15 pF
65 pF
AM dummy antenna
(50 Ω )
antenna jack
Carrier frequency : 999 kHz
30% amplitude
modukation by
1 kHz signal
Output level : 33 dB (44.7 µV)
FM RF signal
generator
set +
–
level mete
r
antenna jack (J1)
4 Ω
Carrier frequency : 98.0 MHz
Output level : 70 dB (3.2 mV)
Mode : stereo
Modulation : main: 1 kHz, 33.75 kHz deviation (45%)
sub: 1 kHz, 33.75 kHz deviation (45%)
19 kHz pilot: 7.5 kHz deviation (10%)
FM Stereo Separation Adjustment
Setting:
SOURCE button: FM
MW Auto Scan/Stop Level Adjustment
Setting:
SOURCE and MODE button: MW
Procedure:
1. Set to the test mode. (See page 17.)
2. Push the SOURCE button and set to FM.
3. Push the MODE button and set to MW.
Display
5. Adjust with the volume RV1 on TU1 so that the “MW” indi-
cation turns to “MWI” indication on the display window.
But, in case of already indicated “MWI”, turn the RV1 so that
put out light “I” indication and adjustment.
Display
4. Push the preset 3 button.
Display
Adjustment Location: See page 20.
Procedure:
FM Stereo Level meter Level meter
signal generator connection reading (dB)
output channel
L-CH L-CH A
B
R-CH L-CH Adjust RV4 on TU1
for minimum reading.
R-CH R-CH C
D
L-CH R-CH Adjust RV4 on TU1
for minimum reading.
L-CH Stereo separation: A-B
R-CH Stereo separation: C-D
The separations of both channels should be equal.
Specification: Separation more than 26 dB
Adjustment Location: See page 20.
INTRO
999

3
SHUF1
MW
INTRO
999

3
SHUF1
MW
INTRO
999

SHUF1
SPEAKER OUT

– 20 –
Adjustment Location:
– SET UPPER VIEW –
RV4 FM Stereo Separation Adjustment
RV1 MW Auto Scan/Stop Level Adjustment
RV2 FM Auto Scan/Stop Level Adjustment
TU1
Tape Speed Adjustment