Electrical Adjustments - Sony LBT-A590 Service Manual

SECTION 2
ELECTRICAL ADJUSTMENTS
Precautions in Repairing
If the front end unit fails, it is difficult to repair the inner circuits,
so replace the entire front end unit.
The FM TUNED level must be adjusted after the AM
TUNED level adjustment has completed.
AM SECTION
AM Tuning Level Adjustment
Setting :
BAND switch : MW (AM)
Loop antenna B
Loop antenna A
AM RF signal
generator
Carrier frequency : 999kHz
30% amplitude
modulation by 400Hz signal
Procedure :
1, Set loop antenna A so that the loop antenna B input level
becomes S8dBy/m.
2. Tune the set to 999kHz.
3. Adjust the RV1 so that the TUNED indicator goes on.
Adjustment Location : TUNER board
FM SECTION
FM Tuning Level Adjustment
Setting :
BAND switch : FM
FM RF stereo signal
generator
75Q coaxial
set
Carrier frequency : 98MHz
Modulation : 1kHz, 75kHz deviation (100%) :
Output level : 30dBy_
FM ANTENNA terminal
Procedure :
1. Tune the set to 93MHz.
2. Adjust RV2 so that the TUNED indicator goes on.
Adjustment Location : TUNER board
FM POLAR Adjustment (CIS model only)
Setting =
BAND switch : FM
FM RF signal
generator
75Q coaxial FM ANTENNA terminal
Carrier frequency : 69@MHz
Output level : imV (60d8p)
1. Connect the frequency counter to the TP1702 and adjust the
RV1702 for a frequency of 31.25kHz + 50Hz.
2. Connect the VTVM to the TP1701, receive the signal of
69MHz + 1kHz (1kHz dev.) and adjust the reading of the
VTVM to OdB,
3. Set the modulation frequency of the FM RF signal generator
to 31.25kHz (10kHz dev.) and adjust the L1701 so that the
reading of the VTVM is OdB.
4. Adjust the RV1701 so that the reading of the VTVM to
14dB.
5. Check that the separation between Pins 13 and 11 of the
CN1701 is more than 18dB.
Adjustment Location : POLAR board