Sony SPP-874, Service Manual, Page: 17 / 38

– 17 –
0 V
Adjust so that they
synchronize at 0 V.
RSSI output waveform
RF signal EXT
signal 20 Hz
RSSI WAVEFORM
FM RF
signal generator
TP502
TP508 (RF GND)
+
–
digital voltmeter
TP503 (RX VT)
TP506 (GND)
SECTION 4
ELECTRICAL ADJUSTMENTS
BASE UNIT SECTION
Note:
• Apply 9V dc from regurated DC power supply.
• Perform the adjustment at T3CH (28CH : 49.910 MHz) as a rule.
• Set to base unit machine test mode. (Refer to page 12.)
• Switch position :
S802 (DIAL MODE) : P (pulse)
TX SECTION ADJUSTMENT
• The electrolytic capacitor (10
µ
F/10 V) connected TP505 (DET
OUT) to TP506 (GND). (Only TX section adjustment)
TX VT Adjustment
Setting :
Procedure :
1. The digital voltmeter connected TP603 (TX VT) to TP506
(GND).
2. Adjust the L602 for 1.1
±
0.1 V reading on the digital voltmeter.
RX VT Adjustment
Setting :
Procedure:
1. The modulation analyzer connected TP502 to TP508 (GND).
2. Adjust the RV601 for 280
µ
W reading on the modulation
analyzer.
Procedure :
1. Adjust the FL501 for the maximam reading on the level meter.
Also check that the output level is the specified values.
Specified Value : –2.6 to –10.6 dBV
RSSI Hi Adjustment
Note:
• Perform the adjustment at T3CH (28CH : 49.910 MHz) as a rule.
Setting :
Procedure :
1. The digital voltmeter connected TP503 (RX VT) to TP506
(GND).
2. Adjust the L503 for 4.0
±
0.1 V reading on the digital voltmeter.
Power Level Adjustment
Note:
• Connect a resistor of 50
Ω
between TP502 and TP508 on Base
main board before adjustment. (See page 18.)
After adjustment, remove the resistor.
Setting:
Procedure :
1. Use the oscilloscope to confirm the FM RF signal generator
input (AF) signal waveform and RSSI signal, and use the RV501
so that they are synchronized (duty is synchronized).
Carrier frequency : 49.910 MHz
Modulation
: 1 kHz
Deviation : FM 3 kHz
Output level : 60 dB
µ
V (1 mV) (EMF)
RX SECTION ADJUSTMENT
RX DISCRI Adjustment
Note:
• Perform the adjustment at T3CH (28CH : 49.910 MHz) as a rule.
Setting :
Carrier frequency : 49.910 MHz
Modulation
: 20 Hz (EXT)
Deviation : AM 50%
Output level : 17 dB
µ
V (7.1
µ
V) (EMF)
+
–
digital voltmeter
TP603 (TX VT)
TP506 (GND)
+
–
modulation
analyzer
TP502
TP508 (GND)
level meter
+
–
PBX tester
TP701
600 Ω
TP702
F.B.
DC 48V
or
FM RF
signal generator
TP502
TP508 (RF GND)
AF oscillator
Output: 20 Hz
+
–
oscilloscope
(DC range)
TP507 (SIG OUT)
TP506 (GND)
Adjustment Location : base main board (See page 18.)