Sony XR-3750 User manual

MICROFILM
XR-3750/C350
AEP Model
UK Model
SERVICE MANUAL
FM/MW/LW CASSETTE CAR STEREO
SPECIFICATIONS
Model Name Using Similar Mechanism NEW
Tape Transport Mechanism Type MG-52A-135
Refer to RM-X2S/X3S SERVICE MANUAL (9-960-039-∏)
issued previously for information of remote commander
(RM-X2S) supplied with XR-C350.
Photo: XR-C350

– 2 –
TABLE OF CONTENTS
1. GENERAL
Location of Controls (XR-3750) ..................................... 3
Location of Controls (XR-C350)..................................... 4
Installation ....................................................................... 5
Connections ..................................................................... 6
2. DISASSEMBLY.......................................................... 10
3. ASSEMBLY OF MECHANISM DECK ........... 12
4. MECHANICAL ADJUSTMENTS ....................... 18
5. ELECTRICAL ADJUSTMENTS
Test Mode ........................................................................ 18
Tape Deck Section ........................................................... 19
Tuner Section................................................................... 19
6. DIAGRAMS
6-1. IC Pin Function Description ............................................ 22
6-2. Printed Wiring Boards –Main Section– ........................... 24
6-3. Schematic Diagram –Main Section– .............................. 27
6-4. Printed Wiring Board –Key Section– ............................. 32
6-5. Schematic Diagram –Key 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.

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

– 4 –

– 5 –

– 6 –

– 7 –

– 8 –

– 9 –

– 10 –
Note: Follow the disassembly procedure in the numerical order given.
FRONT PANEL ASS’Y
1 Push the button
(release)
A
2 Remove the front panel ass’y
to the direction of the arrow A .
COVER ASS’Y
SECTION 2
DISASSEMBLY
2
1
3 cover ass’y
1
2

– 11 –
5 screw
(PTT2.6 × 6)
6 mechanism deck
(MG-52A-135)
4 flexible flat cable
(CN301)
1 three screws
(PTT2.6 × 8)
1 three screws
(PTT2.6 × 8)
2 sub panel
3 connector
(CN302)
SUB PANEL, MECHANISM DECK (MG-52A-135)
MAIN BOARD, HEAT SINK
2 two ground point
screws
1 two screws
(PTT2.6 × 8)
3 main board
5 heat sink
4 screw
(PTT2.6 × 8)
(XR-C350 only)
1 screw (PTT2.6 × 8)
4 screw (PTT2.6 × 8)
(XR-C350 only)
4 six screws
PTT2.6 × 8 : XR-C350
PTT2.6 × 10: XR-3750





– 12 –
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)

– 13 –
CHASSIS (S) ASS’Y
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).
LEVER (MODE)
hole in lever (mode)
¢ mark on rotary switch
lever (mode)
rotary switch
A
C
B

– 14 –
LEVER (PINCH SELECTION)
1 Align.
2 lever (pich 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

– 15 –
LEVER (PINCH) ASS’Y
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
3 Install the spring
(pinch press) to shaft A .
Set the ends of spring to
B and C .
shaft
shaft
B
C
C
B
shaft A
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.
4 Fit claw on B part.
6 Fit projections on D part.
5 Fit projections on C part.
hanger

– 16 –
ARM (SUCTION) 2
Move the arm (suction) in the arrow
direction and fit on projection.
1 Fit the arm (suction) on the shaft.
projection
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)

– 17 –
GEAR (LDG-FT)
2 guide (C)
1 three claws
GUIDE (C)
4 Align hole in the gear (LDG-D) with
¢ mark on the lever (LDG-A).
gear (LDG-FB)
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

– 18 –
SECTION 5
ELECTRICAL ADJUSTMENTS
TEST MODE
This set have the test mode function. In the test mode, FM Auto
Scan/Stop Level andAM (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
erase head rubber belts
capstan idlers
2. Demagnetize the playback head with a head demagnetizer.
3. Do not use a magnetized screwdriver for the adjustments.
4. After the adjustments, apply suitable locking compound to the
parts adjusted.
5. The adjustments should be performed with the power supply
voltage unless otherwise noted.
•Torque 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 CA-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)
Mode Torqu Meter Meter Reading
Forward CQ-403A more than 60 g
Reverse CQ-403R (more than 2.12 oz)
•Tape Tension Measurement

– 19 –
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 21 for the
adjustment.
0 dB=0.775 VTAPE 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 21.
FM RF signal
generator
Carrier frequency : 98.0 MHz
Output level : 22 dB (12.6
µ V)
Mode : mono
Modulation : 1 kHz, 22.5 kHz deviation (30%)
0.01 µ F
set
antenna jack (J1)
Procedure:
1. Set to the test mode. (See page 18).
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
set +–
test tape
WS-48A
(3 kHz, 0 dB)
LINE OUT (XR-C350)
SPEAKER OUT
(
XR-3750
)
10 k Ω (XR-C350)
4
Ω (XR-3750)
speed checker
or
frequency counte
r
Adjustment Location: See page 21.
FM
98.0


SHUF1
FM
98.0
3
SHUF1


– 20 –
FM Stereo Separation Adjustment
Setting:
SOURCE button: FM
FM RF signal
generator
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%)
0.01 µ F
set
antenna jack (J1)
+
–
LINE OUT (XR-C350)
SPEAKER OUT (XR-3750)
level meter
10 k
Ω (XR-C350)
4
Ω (XR-3750)
AM (MW) Auto Scan/Stop Level Adjustment
Setting:
SOURCE and MODE button: MW
AM RF signal
generator
Carrier frequency : 999 kHz
30% amplitude
modulation by
1 kHz signal
Output level : 33 dB
(
44.7
µ
V
)
(50 Ω )set
AM dummy antenna
30 Ω
15 pF
65 pF
antenna jack (J1)
Procedure:
1. Set to the test mode. (See page 18.)
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 21.
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 28dB
Adjustment Location: See page 21.
INTRO
999

3
SHUF1
MW
INTRO
999

3
SHUF1
MW
INTRO 999

SHUF1