Handset - Sony SPP-904 Service Manual

HANDSET

• Make the set in test mode. (See page 9.)
– TX Adjustments and Checks –
1. TX VCO Check
Setting:
digital voltmeter
+
–
Procedure:
1. Connect a digital voltmeter to TP (TX VCO), TP (RX VCO)
and TP (GND) on the HAND RF board.
2. Check that both TP (TX VCO) and TP (RX VCO) voltage of
digital voltmeter are 0.8 V to 2.2 V.
[CHANNEL]
3. Press the key three times to change the channel
to 40CH.
4. Check that both TP (TX VCO) and TP (RX VCO) voltage of
digital voltmeter are 0.8 V to 2.2 V.
[CHANNEL]
5. Press the key once to change the channel to 1CH.
6. Check that both TP (TX VCO) and TP (RX VCO) voltage of
digital voltmeter are 0.8 V to 2.2 V.
2. TX Frequency Adjustment
Setting:
frequency counter
+
–
Procedure:
1. Connect a frequency counter to TP (ANT) and TP (GND) on
the HAND MAIN board.
2. Restart the test mode to change the channel to 21CH.
3. Adjust CT401 on the HAND MAIN board so that the value of
frequency counter becomes 903.052467 MHz ± 600 Hz.
3. TX Power Adjustment
Setting:
power meter
+
–
Procedure:
1. Connect a power meter to TP (ANT) and TP (GND) on the
HAND MAIN board.
2. Adjust RT501 on the HAND RF board so that the value of
power meter becomes –7.5 dBm ± 1 dBm.
[CHANNEL]
3. Press the key three times to change the channel
to 40CH.
4. Check that the value of power meter is –7.5 dBm ± 1.5 dBm.
[CHANNEL]
5. Press the key once to change the channel to 1CH.
6. Check that the value of power meter is –7.5 dBm ± 1.5 dBm.
TP (TX VCO), TP (RX VCO)
TP (GND)
TP (ANT)
TP (GND)
TP (ANT)
TP (GND)
4. Modulation Sensitivity Adjustment
Setting:
AF OSC
+
–
1 kHz, 9 mV
deviation meter
+
–
Procedure:
1. Disconnect the microphone (MC401).
2. Connect an AF OSC to TP (MIC+) and TP (MIC–) on the
HAND MAIN board.
3. Connect a deviation meter to TP (ANT) and TP (GND) on the
HAND MAIN board.
[2]
4. Press the key to change the test mode step to TX MOD
CHECK.
5. Adjust RT403 on the HAND MAIN board so that the value of
deviation meter becomes 8 kHz ± 0.5 kHz.
5. Distortion and S/N Ratio Check
Setting:
AF OSC
+
–
1 kHz, 9 mV
distortion meter
+
–
noise meter
+
–
CCITT: on
Procedure:
1. Connect a distortion meter and noise meter to TP (ANT) and
TP (GND) on the HAND MAIN board.
2. Check that the value of distortion meter is less than 4%.
3. Check that the value of noise meter, and record it.
4. Stop outputting the signal of AF OSC.
5. Check that the value of noise meter again. And check that dif-
ference of level between in step3 and in step5 is less than
30 dB.
TP (MIC+)
TP (MIC–)
TP (ANT)
TP (GND)
TP (MIC+)
TP (MIC–)
TP (ANT)
TP (GND)
13