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Model
XR-C750
Pages
46
Size
846.33 KB
Type
PDF
Document
Service Manual
Brand
Device
Car Audio
File
xr-c750.pdf
Date

Sony XR-C750 Service Manual ▷ View online

– 21 –
GEAR (LDG-FT)
2 tension spring (lever LDG)
5 gear (LDG-FT)
6 polyethylene washer
1 gear (LDG-A)
3 Move the lever (LDG-B)
     in the arrow direction.
gear (LDG-FB)
gear (LDG-D)
hole
gear (LDG-FB)
lever (LDG-A)
4 Align hole in the gear (LDG-D) with
     
¢ mark on the lever (LDG-A).
GUIDE (C)
1 three claws
2 guide (C)
– 22 –
PRECAUTION
1. Wipe the following components with an absorbent cotton cloth
moistened with alcohol before adjustment :
PB head
Pinch roller
Idler
Rubber belt
Capstan
2. Demagnetize the PB head using a head demagnetizer.
3. Be careful not to use a magnetized screwdriver.
4. After the adjustment is completed, lock the adjustment parts using
screws.
5. Unless otherwise specified, make adjustments at the specified
voltage (14.4 V).
Torque Measurement
Mode
Torque Meter
Meter Reading
35 – 65 g • cm
FWD
CQ-102C
(0.49 – 0.90 oz • inch)
FWD
0.5 – 5.0 g • cm
Back Tension
(0.01 – 0.07 oz • inch)
35 – 65 g • cm
REV
CQ-102RC
(0.49 – 0.90 oz • inch)
REV
0.5 – 5.0 g • cm
Back Tension
(0.01 – 0.07 oz • inch)
60 – 200 g • cm
FF, REW
CQ-201B
(0.83 – 2.78 oz • inch)
Tape Tension Measurement
Mode
Tension Meter
Meter Reading
FWD
CQ-403A
more than 60 g
REV
CQ-403R
(more than 2.12 oz)
SECTION 5
ELECTRICAL ADJUSTMENTS
SECTION 4
MECHANICAL ADJUSTMENTS
 See the adjustment location from on page 25 for the adjust-
 ment.
  DECK SECTION
Tape Speed Adjustment
Procedure :
1. Put the set into the FWD PB mode.
speed checker
or
frequency counter
10 k 
set
LINE OUT REAR
test tape
WS-48A
(3 kHz, 0 dB)
Specification : Constant speed
Speed checker
Frequency counter
– 1.5 to + 2.5 %
2,955 to 3,075 Hz
Adjustment Location : See page 25.
DOLBY Level Adjustment
setting :
SHIFT button
: ON (light up SET UP
  and PLAY MODE)
Preset  3  (PLAY MODE) button : NR off
SOUND (BAS) button
: Center
SOUND (TRE) button
: Center
SOUND (BAL) button
: Center
SOUND (FAD) button
: Center
SOUND (VOL) button
: Maximum
Procedure :
1. Put the set into the FWD PB mode.
2. Adjust RV251 (L-CH) and RV261 (R-CH) so that level meter
reading is – 6 ± 0.5 dB (0.37 to 0.41 V).
Adjustment Location : See page 25.
test tape
P-4-D400
(400 Hz, 0 dB)
main board
TP (DOLBY)
set
level meter
L-CH
R-CH
0 dB = 0.775 V
– 23 –
  TUNER SECTION
Cautions during repair
When the tuner unit is defective, replace it by a new one because
its internal block is difficult to repair.
0 dB = 1 µV
Procedure :
1. Set to the test mode.
2. Push the  SOURCE  button and set to FM.
Display
FM Auto Scan/Stop Level Adjustment
Setting :
SOURCE button
: FM
FREQUENCY SELECT switch (E model) : FM 200k
SHUF1
Carrier frequency : 97.9 MHz
Output level
: 22 dB (12.6 µV)
Mode
: mono
Modulation
: 1 kHz, 22.5 kHz deviation (30%)
FM RF signal
generator
0.01 µF
antenna
terminal
set
Note on Adjustment
The adjustments of tuner section, should be performed according to
the following sequence.
1. FM Auto Scan/Stop Level Adjustment
2. FM Stereo Separation Adjustment
3. FM Noise Focus Adjustment (E model)
4. AM (MW) Auto Scan/Stop Level Adjustment
3. Push the preset  3  button.
Display
4. Adjust with the volume RV2 on TU11 so that the “FM” indication
turns to “FM0” indication on the display window.
But, in case of already indicated “FM0”, turn the RV2 so that put
out light “0” indication and adjustment.
Display
SHUF1
Adjustment Location : See page 25.
SHUF1
FM RF signal
generator
antenna
terminal
set
0.01 µF
10 k 
level meter
LINE OUT REAR
FM Stereo Separation Adjustment
Setting :
SOURCE button
: FM
FREQUENCY SELECT switch (E model) : FM 200k
Carrier frequency : 97.9 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%)
L-CH stereo separation : A – B
R-CH stereo separation : C – D
The separations of both channels should be equal.
Specification : Separation more than 28 dB
Adjustment Location : See page 25.
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 TU11 for
minimum reading.
R-CH
R-CH
C
D
L-CH
R-CH
Adjust RV4 on TU11 for
minimum reading.
Procedure :
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 “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.
– 24 –
FM Noise Focus Adjustment (E model)
Setting :
SOURCE button
: FM
FREQUENCY SELECT switch : FM 200k
FM RF signal
generator
antenna
terminal
set
0.01 µF
10 k 
level meter
LINE OUT REAR
Carrier frequency : 97.9 MHz
Output level
: 60 dB (1 mV)
Mode
: mono
Modulation
: 1 kHz, 75 kHz deviation (100%)
Procedure :
1. Tune the 97.9 MHz.
2. The then output level is supposing that 0 dB.
3. Adjust with the volume RV3 on TU11 so that the output level is
– 32 ± 2 dB then signal generator input set to – 20 dB.
Adjustment Location : See page 25.
AM (MW) Auto Scan/Stop Level Adjustment
Setting :
SOURCE 
n MODE button
: AM (US model)
: MW (E model)
FREQUENCY SELECT switch (E model) : MW 10k
Procedure :
1. Set to the test mode. (See page 23.)
2. Push the  SOURCE  button.
3. Push the  MODE  button and set to AM (US model) or MW (E
model).
Display
4. Push the preset  3  button.
Display
5. Adjust with the volume RV1 on TU11 so that the “AM” (US
model) or “MW” (E model) indication turns to “AM0”  (US
model) or “MW0” (E model) indication on the display window.
But, in case of already indicated “AM0” (US model) or “MW0”
(E model), turn the RV1 so that put out light “0” indication and
adjustment.
Display
*1 : E model has the “MW” displayed.
Adjustment Location : See page 25.
SHUF1
*
1
SHUF1
*
1
SHUF1
*
1
AM RF signal
generator
AM dummy
antenna (50 
)
antenna
terminal
set
15 pF
30 
65 pF
Carrier frequency : 1000 kHz
30% amplitude
modulation by
1 kHz signal
output level
: 33 dB (44.7 µV)
Page of 46
Display

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