Electrical Adjustments; Base Unit - Sony SPP-A941 Service Manual

0 dBm = 0.775 V
0 dBv = 1 V

BASE UNIT

Adjustment Equipment and Connection
BASE RF Unit
RF
TP (ANT)
generator
audio
generator
BASE MAIN
Board
feedback
LINE Jack (J7)
bridge
TP14 (TX LOOP VOLTAGE)
TP15 (RX LOOP VOLTAGE)
Setting:
1. Enter the test mode. (refer to page 13)
2. Set the channel to 6ch.
1. RX Loop Voltage Confirmation
1. Connect the digital voltmeter to TP15 (RX LOOP VOLTAGE)
on the BASE MAIN board.
2. Confirm that the value of digital voltmeter is 0.5 Vdc to 4.3
Vdc.
2. TX Loop Voltage Confirmation
1. Connect the digital voltmeter to TP14 (TX LOOP VOLTAGE)
on the BASE MAIN board.
2. Confirm that the value of digital voltmeter is 0.5 Vdc to 4.3
Vdc.
3. TX Frequency Adjustment
1. Connect the RF generator to TP (ANT) on the BASE RF unit.
2. Adjust C15 on the BASE MAIN board for 903.8 MHz ± 3
kHz reading on the RF generator.
4. DEMOD Audio Level Adjustment
1. Connect the RF generator to TP (ANT) on the BASE RF unit.
2. Connect the audio generator (to feedback bridge) to LINE jack
(J7) on the BASE MAIN board.
3. Set the RF generator as follows.
output frequency : 926.55 MHz
output level : –50 dBm
FM deviation : 25 kHz
MOD tone frequency : 1 kHz
4. Adjust VR1 on the BASE MAIN board for –10 ± 1 dBv read-
ing on the audio generator.

ELECTRICAL ADJUSTMENTS

digital
voltmeter
DC 9 V
SECTION 4
5. MOD Deviation Adjustment
1. Connect the RF generator to TP (ANT) on the MAIN RF unit.
2. Connect the audio generator (to feedback bridge) to LINE jack
(J7) on the BASE MAIN board.
3. Set the audio generator as follows.
output level
output frequency: 1 kHz
4. Set the RF generator as follows.
input frequency : 903.8 MHz
filter frequency : 300 Hz to 3 kHz
detector
5. Adjust VR2 on the BASE MAIN board for 25 ± 3 kHz reading
on the RF generator.
– 14 –
: –17 dBv
: PK+1/2