Sony XR-1790 Service Manual ▷ View online
– 13 –
On E model, the tuner section has no adjustments.
Cautions during repair
When the tuner unit is defective, replace it by a new one be-
cause its internal block is difficult to repair.
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 Stereo Separation Adjustment
3. AM Auto Scan/Stop Level Adjustment
2. FM Stereo Separation Adjustment
3. AM Auto Scan/Stop Level Adjustment
FM Auto Scan/Stop Level Adjustment
Setting:
[TUNER]
button: FM 1
FREQUENCY SELECT switch: FM50 k (E model only)
Procedure:
1. Tune the set to 98.0 MHz.
2. Connect the digital voltmeter to TP2 (SD) on MAIN board.
3. Adjust RV2 on TU100 so that the reading on the digital volt-
1. Tune the set to 98.0 MHz.
2. Connect the digital voltmeter to TP2 (SD) on MAIN board.
3. Adjust RV2 on TU100 so that the reading on the digital volt-
meter changes point from low to high.
Adjustment Location: See page 15.
4. Repeat the above adjustment for the REV PB mode.
5. Check that output level difference between FWD PB mode
5. Check that output level difference between FWD PB mode
and REV PB mode is within 4 dB.
Adjustment Location: PB head
Tape Speed Adjustment
Setting:
Procedure:
1. Put the set into the FWD PB mode.
2. Adjust adjustment resistor for inside capstan motor so that the
1. Put the set into the FWD 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.
Specification: Constant speed
Adjustment Location: See page 15.
See the adjustment location from on page 15 for the
adjustment.
adjustment.
Speed checker
Frequency counter
–2 to +3%
2,940 to 3,090 Hz
TUNER SECTION
0 dB=1 µV
FWD
REV
adjustment
screws
screws
+
–
speed checker
or
frequency counter
test tape
WS-48A
(3 kHz, 0 dB)
WS-48A
(3 kHz, 0 dB)
speaker out terminal
set
4
Ω
FM RF signal
generator
dummy
antenna
Carrier frequency : 98.0 MHz
Output level
Output level
: 28 dB (25.1
µ
V)
Mode
: mono
Modulation
: 1 kHz, 22.5 kHz deviation (30%)
antenna
jack (CN900)
jack (CN900)
set
50
Ω
50
Ω
0.1pF
+
–
–
TP2 (SD)
MAIN board
digital
voltmeter
voltmeter
– 14 –
AM Auto Scan/Stop Level Adjustment
Setting:
[TUNER]
button: AM
FREQUENCY SELECT switch: AM 9 k (E model only)
Procedure:
1. Tune the set to 999 kHz
2. Connect the digital voltmeter to TP2 (SD) on MAIN board.
3. Adjust RV1 on TU100 so that the reading on the digital volt-
1. Tune the set to 999 kHz
2. Connect the digital voltmeter to TP2 (SD) on MAIN board.
3. Adjust RV1 on TU100 so that the reading on the digital volt-
meter changes point from low to high.
Adjustment Location: See page 15.
FM Stereo Separation Adjustment
Setting:
[TUNER]
button: FM1
FREQUENCY SELECT switch: FM 50 k (E model only)
Procedure:
L-CH Stereo separation: A-B
R-CH Stereo separation: C-D
The separations of both channels should be equal.
R-CH Stereo separation: C-D
The separations of both channels should be equal.
Specification: Separation more than 26 dB
Adjustment Location: See page 15.
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 TU100
for minimum reading.
R-CH
R-CH
C
D
L-CH
R-CH
Adjust RV4 on TU100
for minimum reading.
FM RF signal
generator
Carrier frequency : 98.0 MHz
Output level
Output level
: 76 dB (6.3 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%)
sub: 1 kHz, 33.75 kHz deviation (45%)
19 kHz pilot: 7.5 kHz deviation (10%)
0.01
µ
F
set
antenna jack (CN900)
+
–
–
speaker out terminal
level meter
4
Ω
AM RF signal
generator
Carrier frequency : 999 kHz
30% amplitude
modulation by
1 kHz signal
Output level
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 (CN900)
+
–
–
TP2 (SD)
MAIN board
digital
voltmeter
voltmeter
– 15 –
Adjustment Location:
Tape Speed Adjustment
RV1 AM Auto Scan/Stop Level Adjustment
TU100
RV2 FM Auto Scan/Stop Level Adjustment
RV4 FM Stereo Separation Adjustment
CN901
S1
FREQUENCY
SELECT
Switch (E model only)
10 k (AM)
200 k (FM)
9 k (AM)
50 k (FM)
↔
TP2 (SD)
– SET BOTTOM VIEW –
– SET UPPER VIEW –
– 16 –
• Waveform
1
IC1
1
(XIN)
2 Vp-p
222 ns
SECTION 5
DIAGRAMS
5-1.
NOTE FOR PRINTED WIRING BOARDS
AND SCHEMATIC DIAGRAMS
AND SCHEMATIC DIAGRAMS
Note on Schematic Diagram:
• All capacitors are in µF unless otherwise noted. pF: µµF
• All capacitors are in µF unless otherwise noted. pF: µµF
50 WV or less are not indicated except for electrolytics
and tantalums.
and tantalums.
• All resistors are in
Ω
and
1
/
4
W or less unless otherwise
specified.
•
¢
: internal component.
•
2
: nonflammable resistor.
•
C
: panel designation.
•
U
: B+ Line.
• Power voltage is dc 14.4V and fed with regulated dc power
supply from ACC and BATT cords.
• Voltages and waveforms are dc with respect to ground
under no-signal (detuned) conditions.
no mark : FM
(
no mark : FM
(
) : AM
[
] : TAPE PLAYBACK
• Voltages are taken with a VOM (Input impedance 10 M
Ω
).
Voltage variations may be noted due to normal produc-
tion tolerances.
tion tolerances.
• Waveforms are taken with a oscilloscope.
Voltage variations may be noted due to normal produc-
tion tolerances.
tion tolerances.
• Circled numbers refer to waveforms.
• Signal path.
• Signal path.
F
: FM
f
: AM
E
: TAPE PLAYBACK
Note on Printed Wiring Board:
• X
: parts extracted from the component side.
• Y
: parts extracted from the conductor side.
•
¢
: internal component.
• b
: Pattern from the side which enables seeing.
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