Connections; Electrical Adjustments; Test Mode; Md Section - Sony MDX-C7900 Service Manual

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 (S700) is "A (ON)" position.
2. Turn ON the regulated power supply. (All LEDs on the set
lights up, and the clock is displayed.)
[OFF]
Note: Press the button, if the clock is not displayed.
[4]
3. Push the preset button.
[5]
4. Push the preset button.
[1]
5. Press the preset button for more than two seconds.
6. Then the display indicates all lights, the test mode is set.
<Release the Test mode>
[OFF]
1. Push the button.
2. Return the "power select" switch (S700) to initially set posi-
tion.
See the adjustment location from on page 20 for the ad-
justment.

MD SECTION

MD section adjustments are done automatically in this set.

TUNER SECTION

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 Stereo Separation Adjustmnet.
3. AM (MW) Auto Scan/Stop Level Adjustment.
4. RDS S-Meter Adjustment.
FM Auto Scan/Stop Level Adjustment
Setting:
[SOURCE]
button: FM
FM RF signal
generator
0.01 F
Carrier frequency: 97.9 MHz (MDX-C7900)
98.0 MHz (MDX-C7900R)
Output level : 22 dB (12.6 V)
Mode : mono
Modulation : 1 kHz, 22.5 kHz deviation (30%)
Procedure:
1. Set to the test mode.
[SOURCE]
2. Push the button and set to FM.
Display
REG
SECTION 4

ELECTRICAL ADJUSTMENTS

0 dB=1 µV
antenna jack (J1)
set
SHUF
*1
3. 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.
REG
*1: MDX-C7900R is indicates "98.00".
Adjustment Location: See page 20.
FM Stereo Separation Adjustment
Setting:
[SOURCE]
button: FM
FM RF signal
generator
antenna jack (J1)
0.01 F
Carrier frequency
Output level
Mode
main
Modulation sub
19 kHz
pilot
Procedure:
FM Stereo
signal generator
output channel
L-CH
R-CH
R-CH
L-CH
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 20.
– 18 –
Display
SHUF
*1
level meter
4
set
speaker out terminal
MDX-C7900 MDX-C7900R
97.9 MHz 98.0 MHz
60 dB (1 mV) 70 dB (3.2 mV)
stereo stereo
1 kHz, 33.75 kHz 1 kHz, 20 kHz
deviation (45%) deviation (22.6%)
1 kHz, 33.75 kHz 1 kHz, 20 kHz
deviation (45%) deviation (22.6%)
7.5 kHz 7.5 kHz
deviation (10%) deviation (10%)
Level meter Level meter
connection reading (dB)
A
L-CH
B
L-CH Adjust RV4 on TU1
for minimum reading.
C
R-CH
D
R-CH Adjust RV4 on TU1
for minimum reading.
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