DOWNLOAD Sony XR-4790 / XR-4800 / XR-7850 (serv.man2) Service Manual ↓ Size: 1 MB | Pages: 33 in PDF or view online for FREE

Model
XR-4790 XR-4800 XR-7850 (serv.man2)
Pages
33
Size
1 MB
Type
PDF
Document
Service Manual
Brand
Device
Car Audio
File
xr-4790-xr-4800-xr-7850-sm2.pdf
Date
PREV: Sony XR-4790 / XR-4800 / XR-7850 Service Manual

Sony XR-4790 / XR-4800 / XR-7850 (serv.man2) Service Manual ▷ View online

– 13 –
SECTION  4
MECHANICAL  ADJUSTMENTS
SECTION  5
ELECTRICAL  ADJUSTMENTS
1. Clean the following parts with a denatured-alcohol-moistened
swab:
playback head
pinch roller
rubber belt
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-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
Mode
Torqu Meter
Meter Reading
Forward
CQ-102C
30 - 65 g•cm
(0.42 - 0.90 oz•inch)
Forward
CQ-102C
0.5 - 4.5g•cm
Back Tension
(0.01 - 0.06 oz•inch)
Reverse
CQ-102RC
30 - 65 g•cm
(0.42 - 0.90 oz•inch)
Reverse
CA-102RC
0.5 - 4.5g•cm
Back Tension
(0.01 - 0.06 oz•inch)
FF, REW
CQ-201B
60 - 200 g•cm
(0.83 - 2.78 oz•inch)
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 (S801) 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 (S801) 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 3,075Hz
Procedure:
1. Put the set into the FWD PB mode.
2. Adjust adjustment resistor for inside capastan motor so that
the reading on the speed checker or frequency counter becomes
in specification.
Specification: Constant speed
+
–
test tape
WS-48A
(3 kHz, 0 dB)
speed checker
or
frequency counter
10 k
Ω
 
set
LINE OUT 
Adjustment Location: See page 16.
– 14 –
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.
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
FM
 
98.0
SHUF1
FM Noise Focus Adjustment
Setting:
[SOURCE]
 button: FM
Procedure:
1. Tune the 98.00 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 RF signal
generator
Carrier frequency : 98.00 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 
Ω
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.
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 
level meter
10  
Ω
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 16.
– 15 –
AM (MW) Auto Scan/Stop Level Adjustment
Make this adjustment after "FM Auto Scan/Stop Level Adjustment".
Setting:
[SOURCE]
 and 
[MODE]
 button: MW
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
4. 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
Adjustment Location: See page 16.
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)
MW
INTRO
999
 
SHUF1
INTRO
999
SHUF1
– 16 –
Adjustment Location:
RV1 AM (MW) Auto Scan/Stop Level Adjustment
RV2 FM  Auto Scan/Stop Level Adjustment
RV3 FM  Noise Focus Adjustment
RV4 FM  Stereo Separation Adjustment
Tape Speed Adjustment
TU1
—SET UPPER VIEW–
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