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Model
XR-3750 XR-3758 XR-3759 XR-7750 XRS-888
Pages
36
Size
2.36 MB
Type
PDF
Document
Service Manual
Brand
Device
Car Audio
File
xr-3750-xr-3758-xr-3759-xr-7750-xrs-888.pdf
Date
PREV: Sony XR-3750 / XR-3758 / XR-3759 / XR-7750 / XR-C350 / XRS-888 (serv.man2) Service Manual

Sony XR-3750 / XR-3758 / XR-3759 / XR-7750 / XRS-888 Service Manual ▷ View online

– 13 –
SECTION  4
MECHANICAL  ADJUSTMENTS
SECTION  5
ELECTRICAL  ADJUSTMENTS
1. Clean the following parts with a denatured-alcohol-moistene
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. 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
Tension Meter
Meter Reading
Forward
CQ-403A
more than 90 g
(more than 3.18 oz)
Reverse
CQ-403R
more than 90 g
(more than 3.18 oz)
•
 Tape Tension  Measurement
TEST  MODE
This set have the test mode function. In the test mode, FM Auto
Scan/Stop Level and AM (MW) Auto Scan/Stop Level adjustments
can be performed easier than it in ordinary procedure.
<Set the Test Mode>
1. Set the “power select” switch (S501) is “A” position.
2. Turn ON the regulated power supply. (All LEDs on the set
lights up, and the clock is displayed)
Note: Press the 
[OFF]
 button, if the clock is not displayed.
3. Push the preset 
[4]
 button.
4. Push the preset
[5]
 button.
5. Press the preset 
[1]
 button for more than two seconds.
6. Then the display indicates all lights, the test mode is set.
<Release the Test mode>
1. Push the 
[OFF]
 button.
2. Return the “power select” switch (S501) to initially set posi-
tion.
See the adjustment location from on page 16 for the
adjustment.
0 dB=0.775 V
TAPE  DECK  SECTION
Tape Speed Adjustment
Setting:
Speed checker
Frequency counter
–1.5 to +2.5%
2,955 to 3,075 Hz
Procedure:
1. Put the set into the PB mode.
2. Adjust adjustment resistor for inside capstan motor so that the
reading on the speed checker or frequency counter becomes in
specification.
Specification: Constant speed
Adjustment Location: See page 16.
set
+
–
test tape
WS-48A
(3 kHz, 0 dB)
LINE OUT
10 k 
Ω
speed checker
or
frequency counter
Mode
Torque Meter
Meter Reading
Forward
CQ-102C
30 – 65 g•cm
(0.42 – 0.90 oz·inch)
Forward
CQ-102C
0.5 – 4.5 g•cm
Back Tension
(0.01 – 0.06 oz·inch)
Reverse
CQ-102RC
30 – 65 g•cm
(0.42 – 0.90 oz·inch)
Reverse
CQ-102RC
0.5 – 4.5 g•cm
Back Tension
(0.01 – 0.06 oz·inch)
FF, REW
CQ-201B
60 – 200 g•cm
(0.83 – 2.78 oz·inch)
– 14 –
TUNER  SECTION
98.0
SHUF1
Cautions during repair
When the tuner unit is defective, replace it by a new one be-
cause its internal block is difficult to repair.
Note:
Adjust the tuner section in the sequence shown below.
1. FM Auto Scan/Stop Level Adjustment
2. FM Noise Focus Adjustment
3. FM Stereo Separation Adjustment
4. AM (MW) Auto Scan/Stop Level Adjustment
FM Auto Scan/Stop Level Adjustment
Setting:
[SOURCE]
 button: FM
Procedure:
1. Set to the test mode. (See page 13)
2. Push the 
[SOURCE]
 button and set to FM.
Display
3. 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 16.
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)
FM
98.0
SHUF1
 0 dB=1 µV
FM Noise Focus Adjustment
Setting:
[SOURCE]
 button: FM
Procedure:
1. Tune the 98.0 MHz.
2. The then output level is supposing that (A) dB.
3. Adjust with the volume RV3 on TU1 so that the output level is
(A) –32 ± 2 dB then signal generator input set to –20 dB.
Adjustment Location: See page 16.
FM Stereo Separation Adjustment
Setting:
[SOURCE]
 button: FM
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 30 dB
Adjustment Location: See page 16.
FM RF signal
generator
Carrier frequency : 98.0 MHz
Output level
: 60 dB (1 mV)
Mode
: mono
Modulation
: 1 kHz, 75 kHz deviation (100%)
0.01 
µ
F
set
antenna jack (J1)
+
–
LINE  OUT
level meter
10 k 
Ω
FM RF signal
generator
Carrier frequency : 98.0 MHz
Output level
: 60 dB (1 mV)
Mode
: mono
Modulation
: 1 kHz, 75 kHz deviation (100%)
0.01 
µ
F
set
antenna jack (J1)
+
–
LINE  OUT
level meter
10 k 
Ω
– 15 –
AM (MW) Auto Scan/Stop Level Adjustment
Make this adjustment after “FM Auto Scan/Stop Level Adjustment”.
Setting:
[SOURCE]
and
[MODE]
button: MW
AM RF signal
generator
Carrier frequency : 999kHz
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 13)
2. Push the
[SOURCE]
button and set to FM.
3. Push the
[MODE]
button and set to MW.
Display
MW
999
SHUF1
INTRO
4. Adjust with the volume RV1 on TU1 so that the “MW” indica-
tion 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
999
SHUF1
INTRO
Adjustment Location: See page 16.
– 16 –
Adjustment Location:
– SET  UPPER  VIEW –
Tape Speed Adjustment
TU 1
RV 1 AM (MW) Auto Scan/Stop Level Adjustment
RV 2 FM Auto Scan/Stop Level Adjustment
RV 3 FM Noise Focus Adjustment
RV 4 FM Stereo Separation Adjustment
Page of 36
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