20
HCD-VX888
FM Tuned Level Adjustment
Procedure:
1.
Supply a 98 MHz signal at 28 dB from the ANTENNA terminal.
2.
Tune the set to 98 MHz.
3.
Adjust RV11 to the point (moment) when the TUNED indicator
will change from going off to going on.
Adjustment Location: MAIN board
Null Adjustment
Procedure:
1.
Supply a 98 MHz signal at 60 dB from the ANTENNA terminal.
2.
Tune the set to 98 MHz.
3.
Measure voltage between pin 22 and pin 3 of IC11. Adjust
T11 until the voltage becomes 0 V.
Adjustment Location: MAIN board
FM RF SIGNAL GENERATOR
75
Ω
coaxial
Carrier frequency : 98 MHz
Modulation : AUDIO 1 kHz, 75 kHz
deviation (100%)
Output level : 28 dB (at 75
Ω
open)
FM ANTENNA terminal
(TM1)
set
FM RF SIGNAL GENERATOR
75
Ω
coaxial
Carrier frequency : 98 MHz
Modulation : AUDIO 1 kHz, 75 kHz
deviation (100%)
Output level : 60 dB (at 75
Ω
open)
FM ANTENNA terminal
(TM1)
set
CN301
RV301
RV302
RV303
RV351
RV304
RV354
NO303
CN304
3 1
FM TUNED LEVEL
TUNER SECTION
CD SECTION
Note :
1. CD Block is basically designed to operate without adjustment.
Therefore, check each item in order given.
2. Use YEDS-18 disc (3-702-101-01) unless otherwise indicated.
3. Use an oscilloscope with more than 10M
Ω
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.
S-Curve Check
Procedure :
1. Connect oscilloscope to TP (FEO).
2. Connect between TP (FEI) and TP (VC) by lead wire.
3. Turn Power switch on.
4. Load a disc (YEDS-18) and actuate the focus search. (In
consequence of open and close the disc tray, actuate the focus
search)
5. Confirm that the oscilloscope waveform (S-curve) is
symmetrical between A and B. And confirm peak to peak level
within 4
±
1 Vp-p.
7. After check, remove the lead wire connected in step 2.
Note :
• Try to measure several times to make sure than the ratio
of A : B or B : A is more than 10 : 7.
• Take sweep time as long as possible and light up the
brightness to obtain best waveform.
RF Level Check
Procedure :
1. Connect oscilloscope to TP (RFAC).
2. Turned Power switch on.
3. Load a disc (YEDS-18) and playback.
4. Confirm that oscilloscope waveform is clear and check RF signal
level is correct or not.
5. Measure the RFDC in the same way.
BD board
Oscilloscope
TP(FEO)
TP(DVC)
symmetry
S-curve waveform
within 4
±
1Vp-p
A
B
TP(RFAC)
TP(DVC)
BD board
oscilloscope
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TEL 13942296513 QQ 376315150 892498299
