Sony HCD-GT22 Service Manual page 21

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TUNER SECTION
FM TUNE LEVEL CHECK
signal
generator
Procedure:
1. Turn on the set.
2. Input the following signal from signal generator to FM antenna
input directly.
Carrier frequency: A = 87.5 MHz, B = 98 MHz, C = 108 MHz
Deviation
Modulation
ANT input
Note: Use 75 ohm coaxial cable to connect signal generator and the set.
You cannot use video cable for checking.
Use signal generator whose output impedance is 75 ohm.
3. Set to FM tuner function and tune A, B and C signals.
4. Confirm "TUNED" is lit on the display for A, B and C signals.
When the selected station signal is received in good condition,
"TUNED" is displayed.
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set
: 75 kHz
: 1 kHz
: 35 dBu (EMF)
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CD SECTION
Note:
1. CD Block is basically constructed to operate without adjustment.
2. Use YEDS-18 disc (3-702-101-01) unless otherwise indicated.
3. Use an oscilloscope with more than 10 MΩ impedance.
4. Clean the object lens by an applicator with neutral detergent when the
signal level is low than specified value with the following checks.
5. Check the focus bias check when optical pick-up block is replaced.
FOCUS BIAS CHECK
TP121 (RFI)
TP124 (VC)
Procedure :
1. Connect oscilloscope to TP121 (RFI) and TP124 (VC) on the
CD board.
2. Press the I/1 button to turn the power ON.
3. Set disc (YEDS-18) on the tray and press the u button to
playback.
4. Confirm that oscilloscope waveform is as shown in the figure
below. (eye pattern)
A good eye pattern means that the diamond shape (◊) in the
center of the waveform can be clearly distinguished.
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Checking Location:
– CD Board (Conductor Side) –
TP124
(VC)
TP121
(RFI)
IC101
co
.
HCD-GT22/GT44/GT55
9 4 2 8
oscilloscope
(DC range)
CD board
+
–
VOLT/DIV: 200 mV
TIME/DIV: 500 ns
0 5 8 2 9 9 4 2 8
level:
1.2 ± 0.3 Vp-p
m
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