Electrical Adjustments - Sony STR-W77 Service Manual

Precautions in Repairing
The adjustment should be performed in the publication.
Note. 1 :
(MW n FM n SW)
Note. 2 : As a front-end (FE1) is difficult to repair if faulty, replace
it with new one.
r Abbreviation
AUS : Australian
EA : Saudi Arabia
SP : Singapore
MY : Malaysia
CND : Canadian
E2 : Tuner sections SW BAND do not exist.
E3 : Tuner sections SW BAND exist.
MW SECTION
MW Tuned Indication Lighting Level
Setting :
Band : MW
loop antenna A
AM RF signal
generator
Carrier frequency : 999kHz (at 9kHz step)
1,050kHz (at 10kHz step)
Procedure :
1. Set loop antenna A so that the loop antenna B input level becomes
55dBµ/m (0.6mV/m)
2. Tune the set to 999kHz or 1,050kHz.
3. Adjust RV41 so that the TUNED indicatior goes on.
FM SECTION
FM Tuned Indication Lighting Level
Note : Always make the tuning level adjustment first.
(Since it affects the FM tuning level.)
Setting :
Band : FW
FM RF stereo signal
generator
75 Ω coaxial
Carrier frequency : 98MHz
Modulation : OFF
Output level : 0.018mV (25dB )
Procedure :
1. Tune the set to 98MHz.
2. Adjust RV42 so that the TUNED indicator goes on.
SECTION 3

ELECTRICAL ADJUSTMENTS

AR : Argentine
HK : Hong Kong
JE : Tourist
TH : Thailand
loop antenna B
set
FM ANTENNA terminal
set
SW Control Voltage Adjustment
(Frequency Coverge Adjustment)
(E3, EA, MY, SP, HK, JE model)
Setting :
Band : SW
Procedure :
1. Connect digital Voltmeter to diode D1 center lead and ground.
2. Adjust for a following value reading on digital Voltmeter.
Set frequency
5.95MHz
SW
17.9MHz
SW Tracking Adjustment
(E3, EA, MY, SP, HK, JE model)
Setting :
Band : SW
AM RF signal
generator
Modulation : 400Hz
30% modulation
Procedure :
Adjust for maximum reading on VTVM.
Set frequency
7MHz
SW
17MHz
Repeat the procedures is each adjustment several times, and the
r
frequency coverage and tracking adjustment should be finally done
by the trimmer capacitors.
Adjustment Location : TCB board
– 6 –
Adjustment Reading on digital
part voltmeter
T2 1.2Vdc
CV2 8.5Vdc
VTVM
+
set
–
SPEAKER terminal
AM ANTENNA terminal
Adjustment
part
T1
CV1