Electrical Adjustment - Sony ST-SB920 Service Manual

Precautions in Repairing
If the front end unit fails, it is difficult to repair the inner circuits, so
replace the entire front end unit.
Set "IF : WIDE" after the all adjustments.
FM SECTION 0dB = 1µV
FM RF SSG
FM ANTENNA (75 Ω )
•
Standard Setting of FM Stereo RF Signal Generator.
STEREO STANDARD SIGNAL
Carrier frequency : 98MHz
Modulation : Audio 1kHz
Main channel (L+R) : 33.75kHz
deviation
Sub channel (L–R) : 33.75kHz
deviation
Pilot : 7.5kHz
Deviation
How to switch IF BAND : WIDE/NARROW and ANT
ATT : ON/OFF
Method 1:
1. Set the reception mode to FM.
2. Push the MENU button and turn the TUNING/SELECT to
indicate "Reception" on the fluorecent display tube, then press
the ENTER button.
3. Rotate the TUNING/SELECT knob in the clokwise direction.
(Proceeds onto the step 5 when rotated in the counterclokwise
direction.)
4. Turn the TUNING/SELECT knob to indicate "ANT ATT :
OFF" on the fluorescent display tube, then press the
button.
5. Turn the TUNING/SELECT knob to indicate "IF : NARROW"
or "IF : WIDE" on the fluorescent display tube, then press the
lENTER button.
When the IF BAND : NARROW is set, "NARROW" is
indicated on the fluorescent display tube.
6. Set WIDE after the operation.
* When set to standby for inputs using the
knob, "SELECT" is indicated on the fluorecent display tube.
Method 2:
After the test modes "2. Display Tube Check and KEY Check mode"
or "3. Entering the Factory Preset", "IF : NARROW" and "IF :
WIDE" are switched every time pressing RETURN button the IF
BAND : NARROW is set "NARROW" is indicated on the
fluorescent display tube.
Likewise, the mode can be switched between "ANT ATT : ON"
and "ANT ATT : OFF". When set to ANT ATT : ON, the fluorescent
display tube indicates ANT ATT.
SECTION 3
ELECTRICAL ADJUSTMENTS
1kHz
distortion meter
highpass
filter
set
LINE OUT
MONAURAL
STANDARD SIGNAL
Carrier frequency : 98MHz
Modulation : Audio 1kHz
75kHz deviation
ENTERl
TUNING/SELECTl
FM Discriminator ADJUSTMENT
(NULL and MONO Distortion Adjustment)
Setting:
IF BAND : WIDE
ANT ATT : OFF
FM RF SSG
FM ANTENNA (75 Ω )
Modulation : Monaural Standard signal
Output level : 6mV (76dB) (at 75 Ω open)
TP251
NULL terminal
Procedure:
1. Tune the set to 98 MHz.
2. Adjust IFT252 for 0V reading on the digital voltmeter.
................... NULL
3. Adjust IFT253 for a minimum reading on the distortion meter.
................... MONO Distortion (THD)
4. Repeat the adjustments of 2 and 3 several times.
Note : When replacing the ceramic filter, perform this alignment.
— 5 —
1kHz
distortion meter
highpass
filter
set
LINE OUT
Digital Voltmeter
(DC range)