Sony ICF-CD873 Service Manual ▷ View online
– 9 –
AM IF ADJUSTMENT
Adjust for a maximum reading on level meter
T1
450 kHz
AM FREQUENCY COVERAGE ADJUSTMENT
Adjustment Part
Frequency Display
Reading on Digital Voltmeter
L4
530 kHz
2.8 V
Confirmation
1,710 kHz
9.5V
AM TRACKING ADJUSTMENT
Adjust for a maximum reading on level meter
L3
580 kHz
CT2
1,490 kHz
FM FREQUENCY COVERAGE ADJUSTMENT
Adjustment Part
Frequency Display
Reading on Digital Voltmeter
L2
87.5 MHz
2.1 V
Confirmation
108 MHz
8.5 V
FM TRACKING ADJUSTMENT
Adjust for a maximum reading on level meter
L1
87.5 MHz
CT1
108 MHz
Adjustment Location: MAIN board (See page 11)
FM VCO Adjustment
Setting:
Procedure:
1. Connect the frequency counter to TP7, 8 as shown the figure
1. Connect the frequency counter to TP7, 8 as shown the figure
below.
2. Tune the set to 98 MHz.
3. Adjust RV1 for 76 kHz reading on the frequency counter.
3. Adjust RV1 for 76 kHz reading on the frequency counter.
Specified Value: 75.95 to 76.05 kHz
Adjustment Location: MAIN board (See page 13)
SECTION 5
ELECTRICAL ADJUSTMENTS
TUNER SECTION
0 dB=1 µV
[AM]
Setting:
Function
Function
: RADIO
Band switch : AM
[FM]
Setting:
Function
Function
: RADIO
Band switch : FM
• Repeat the procedures in each adjustment several times, and the
frequency coverage and tracking adjustments should be finally
done by the trimmer capacitors.
done by the trimmer capacitors.
• Remove FM antenna in FM adjustments.
AM RF signal
generator
30% amplitude
modulation by
400 Hz signal
Output level: as low as possible
modulation by
400 Hz signal
Output level: as low as possible
Put the lead-wire
antenna close to
the set.
antenna close to
the set.
+
–
–
level meter
set
32
Ω
2
jack (J301)
FM RF signal
generator
22.5 kHz frequency
deviation by 400 Hz
signal
Output level: as low as possible
deviation by 400 Hz
signal
Output level: as low as possible
+
–
–
level meter
2
jack (J301)
set
32
Ω
0.01
µ
F
MAIN board
TP12 (FM IN)
TP12 (FM IN)
digital voltmeter
100 k
Ω
MAIN board
TP53 (VT)
FM RF SSG
Carrier frequency: 98 MHz
Modulation: 400 Hz, 30% FM modulation
Output level: 0.1 V (100 dB)
Modulation: 400 Hz, 30% FM modulation
Output level: 0.1 V (100 dB)
MAIN board
TP12 (FM IN)
TP12 (FM IN)
0.01
µ
F
set
1
µ
F
TP8 (VCO)
+
–
–
frequency counter
33 k
Ω
TP7 (+B)
+
MAIN board
– 10 –
CD SECTION
Note:
Tracking Balance Adjustment and Tracking Gain Adjustment are
done automatically in this set.
Tracking Balance Adjustment and Tracking Gain Adjustment are
done automatically in this set.
TEST MODE
1. Press the CD LID OPEN/CLOSE DET switch (S424) on the
PUSH SWITCH board.
2. Under standby condition (when the clock appear in the dis-
play), short the BP (CD TEST AUTO).
Note:
If the power is supplied to the microprocessor once, it is backed up
for 3 minutes, therefore the TEST mode will not be activated within
3 minutes even if the power is turned on again. In this case, short
instantaneously the BP (CD TEST MANUAL).
3 minutes even if the power is turned on again. In this case, short
instantaneously the BP (CD TEST MANUAL).
3. Press the ^ key, and the focus search is repeated.
At this time, check that the optical pick-up objective lens moves
smoothly without a sticking or noise.
smoothly without a sticking or noise.
4. Load the test disc (YEDS-18: Part No. 3-702-101-01), and per-
form automatic adjustment after the focus search succeded.
5. After automatic adjustment is finished, move the sled motor
to the center. At this time, keep pressing the + and =
keys to confirm that optical pick-up moves smoothly via most
inside track
keys to confirm that optical pick-up moves smoothly via most
inside track
→
most outside track
→
most inside track with-
out a sticking or noise.
6. Confirm the traverse waveform.
7. Press the [WAKE UP TRACK] key.
8. The tracking servo and the sled servo are turned on, the mute
7. Press the [WAKE UP TRACK] key.
8. The tracking servo and the sled servo are turned on, the mute
is cancelled.
9. Playback the 2nd track.
10. Adjust the RF and jitter waveforms.
10. Adjust the RF and jitter waveforms.
Connecting points: MAIN Board (See page 13)
Focus Bias Adjustment
This adjustment is to be done when the optical block is replaced.
Connection:
Adjustment Procedure:
1. Connect the oscilloscope to TP504 (VREF) and TP503 (RF)
1. Connect the oscilloscope to TP504 (VREF) and TP503 (RF)
on the MAIN board.
2. Insert the test disc (YEDS-18: Part No.3-702-101-01) and press
^ key to play.
3. Move the optical pick-up to the music area on the disc to en-
able easy visibility of the eye pattern by + or = key
pressing.
pressing.
4. Adjust RV501 so that the 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.
A good eye pattern means that the diamond shape (≈) in the
center of the waveform can be clearly distinguished.
• RF signal reference waveform (eye pattern)
Adjustment Location: MAIN Board (See page 13)
MAIN board
TP503 (RF)
TP504 (VREF)
+
–
–
oscilloscope
(AC range)
VOLT/DIV: 0.2 V
TIME/DIV: 500 ns
TIME/DIV: 500 ns
1.3
±
0.5 Vp-p
When observing the eye pattern, set the oscilloscope
for AC range and raise vertical sensitivity.
for AC range and raise vertical sensitivity.
– 11 –
Focus Gain Adjustment
A frequency response analyzer is necessary in order to perform
this adjustment exactly.
However, this gain has a margin, so even if it is slightly off, there
is no problem. Therefore, do not perform this adjustment.
Focus gain determines the optical pick-up follow-up (vertical and
horizontal) relative to mechanical noise and mechanical shock
when the 2-axis device operate.
However, as these reciprocate, the adjustment is at the point where
both are satisfied.
• When gain is raised, the noise when the 2-axis device operates
this adjustment exactly.
However, this gain has a margin, so even if it is slightly off, there
is no problem. Therefore, do not perform this adjustment.
Focus gain determines the optical pick-up follow-up (vertical and
horizontal) relative to mechanical noise and mechanical shock
when the 2-axis device operate.
However, as these reciprocate, the adjustment is at the point where
both are satisfied.
• When gain is raised, the noise when the 2-axis device operates
increases.
• When gain is lowered, mechanical shock and skipping occurs
more easily.
• When gain adjustment is off, the symptoms below appear.
The following is a simple adjustment method.
– Primary Adjustment –
Note:
Since exact adjustment cannot be performed, remember the posi-
tions of the controls before performing the adjustment. If the posi-
tions after the primary adjustment are only a little different, return
the controls to the original position.
tions of the controls before performing the adjustment. If the posi-
tions after the primary adjustment are only a little different, return
the controls to the original position.
Connection:
• The time until music starts becomes longer for
STOP
→
PLAY or automatic selection.
(=, + buttons pressed)
(Normally takes about 2 seconds)
(Normally takes about 2 seconds)
• Music does not start and disc continues to
rotate for STOP
→
PLAY or automatic
selection.
(=, + buttons pressed)
(=, + buttons pressed)
• Sound is interrupted during PLAY.
Or time counter display stops progressing.
• More noise during 2-axis device operation
Gain
Focus
Symptoms
low
–
–
high
Procedure:
1. Keep the set horizontal.
1. Keep the set horizontal.
If the set is not horizontal, this adjustment cannot be per-
formed due to the gravity against the 2-axis device
formed due to the gravity against the 2-axis device
2. Insert the test disc (YEDS-18) and press the ^ button.
3. Connect the oscilloscope BT (FEO) and TP504 (VREF) on
3. Connect the oscilloscope BT (FEO) and TP504 (VREF) on
the MAIN board.
4. Adjustment RV502 on the MAIN board so that the waveform
is as shown in the figure below.
• Incorrect Examples (DC level changes more than on adjusted
waveform)
)
(
VOLT/DIV: 100 mV
TIME/DIV: 2 mS
TIME/DIV: 2 mS
100 mV
0 V
VOLT/DIV: 100 mV
TIME/DIV: 2 mS
TIME/DIV: 2 mS
200 mV
0 V
VOLT/DIV: 100 mV
TIME/DIV: 2 mS
TIME/DIV: 2 mS
75 mV
0 V
low focus gain
high focus gain
MAIN board
BP (FEO)
TP504 (VREF)
+
–
–
oscilloscope
Adjustment Location: MAIN Board (See page 13)
– 12 –
MAIN CLOCK SECTION
Main Clock Adjustment
Connection:
Adjustment jig:
Procedure:
1. Connect the frequency counter as the above figures.
2. Adjust CT401 for 4.2495 MHz reading on the frequency
1. Connect the frequency counter as the above figures.
2. Adjust CT401 for 4.2495 MHz reading on the frequency
counter.
Specified Value: 4.2490 to 4.2500 MHz
+
–
–
adjustment
jig
10 : 1 probe
TP (+5 V)
TP401 (4.194 MHz)
TP GND (SHIELD)
+5
IN
GND
IN
GND
frequency counter
MAIN board
OUT
GND
GND
1 M
Ω
100 k
Ω
100 k
Ω
+5 V
0.5 pF
47 uF
IN
GND
1000 pF
1 M
Ω
OUT
GND
INVERTER
(TC7W04F)
(TC7W04F)
+
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