Sony MDX-C670, Service Manual

Page: 12 / 59

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SECTION 4
ELECTRICAL ADJUSTMENTS
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 (S702) is “ON” 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.
4. Adjust with the volume RV2 on TU1 so that the “FM” indica-
tion 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
Adjustment Location: See page 14.
TUNER SECTION
0dB=1µV
Cautions during repair
When the tuner unit is defective, replace it by a new one because
its internal block is difficult to repair.
FM Auto Scan/Stop Level Adjustment
Setting:
SOURCE button: FM
Procedure:
1. Set to the test mode. (See page 12).
2. Push the SOURCE button and set to FM.
Display
3. Push the preset 3 button.
Display
MD SECTION
MD section adjustments are done automatically in this set.
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 30dB
Adjustment Location: See page 14.
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
terminal
SHUF1
REG
SHUF1
REG
SHUF1
REG
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%)
0.01µF
+
–
LINE OUT
VTVM
10 k
Ω
set
antenna
terminal
sub: 1 kHz, 33.75 kHz deviation (45%)
19 kHz pilot: 7.5 kHz deviation (10%)