Electrical Adjustments; Check And Adjustment (Mrd-Rf915R); Carrier Modulation Check (Mrd-Rf915R); Separation Check (Mrd-Rf915R) - Sony MDR-RF915R Service Manual

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MRD-RF915R
Notes:
1. Use transmitter with check and adjustment alreadycompleted.
2. On adjusting the headphones section, use the transmitter as a
jig.
Headphones:MDR-RF915R
Transmitter:TMR-RF915R
Procedure:
1. Connect an oscillator with attenuator and terminator (600 Ω)
to the transmitter AUDIO IN-A connector (J402).
2. Connect an AC adapter to the transmitter DC IN 9V jack (J404).
3. Connect a DC 2.4V to the +B power line externally.
4. Connect lead wires to IC301 pin 4, pin 6, pin 7 and GND on
the RX-BASE board.
5. Connect a resistor 33k Ω between IC301 pin 4 and pin 7.
6. Connect lead wires to the speakers' terminals (L+,L-,R+,R-)
on the RX-BASE board.
3-1. Free Run Frequency Check and Adjustment
1. Set the transmitter AUDIO IN-A connector (J402) to no signal.
Note: In this case, operation time is about 5 or 10 minutes.
Perform confirmation for less than 5 minutes.
2. Check the transmitter power indicator (red) lights.
3. Set the transmitter CHANNEL switch to 1.
4. Set the RV303 (TUNE) to the center position.
5. Connect a frequency counter to IC301 pin 4 and GND on the
RX-BASE board, then confirm the frequency within 76kHz
± 50Hz
6. When the frequency dose not satisfy the specified value, adjust
the value of the frequency counter to specification by RV301
on the RX-BASE board.
Specified values: 76kHz ± 50Hz.
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L 13942296513
7. Remove a 33 Ω resister between IC301 pin 4 and pin 7.
Setting :
Frequency counter
3-2. Receive Frequency Check and Adjustment
1. Set the transmitter CHANNEL switch to 2.
2. Set the transmitter NOISE FILTER switch to OFF.
3. Input a signal of 1kHz, 316mVrms to transmitter AUDIO IN-
A(L-ch) connector only.
4. Keep distance between transmitter and headphones to 5 meters
over.
5. Set the headphones volume (RV302) to minimum.
6. Set the RV303 (TUNE) to the center position.
7. Connect an oscilloscope CH1 and CH2 to IC301 pin 6 and
pin 4.
8. Check the waveform of the oscilloscope to CH1 is demodulated
1kHz signal and CH2 is GND.
9. If CH1 and CH2 are not satisfied in step 8, adjust the coil (L301)
on the RX board to satisfied step 8.
10. Set the transmitter CHANNEL switch to 1.
11. Adjust the RV303 (TUNE) to receive a signal.
Confirm the signal with stereo.
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12. Check same step 8.
13. Set the transmitter CHANNEL switch to 3.
14. Adjust the RV303 (TUNE) to receive a signal.
Confirm the signal with stereo.
.
15. Check same step 8.
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ELECTRICAL ADJUSTMENTS

IC301 pin4
+
–
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SECTION 3
2 9
8
Setting :
IC301 pin6
3-3. Carrier Modulation Check
1. Set the transmitter CHANNEL switch to 2.
2. Set the transmitter NOISE FILTER switch to OFF.
3. Input a signal of 1kHz, 316mVrms to transmitter AUDIO IN-A
(L-ch) connector only.
4. Set the headphones volume (RV302) to minimum.
5. Connect an oscilloscope CH1 and CH2 to IC301 pin 6 and
pin 4.
6. Adjust the tuning control (RV303) to receive radio frequency.
7. Check the waveform of the oscilloscope that the CH1 is
demodulated 1kHz signal and CH2 is GND.
8. Connect an AC voltmeter with LPF to IC301 pin 6 and GND.
9. Check the value of the AC voltmeter to 26mVrms ± 2mV
Setting :
Digital voltmeter
(AC range)
LPF
2.2K
+
–
Q Q
3-4. Separation Check
3 6 7 1 3 1 5
1. Set the transmitter CHANNEL switch to 2.
2. Set the transmitter NOISE FILTER switch to OFF.
3. Input a signal of 1kHz, 316mVrms to transmitter AUDIO IN-A
(L-ch) connector only.
4. Connect an oscilloscope CH1 to speakers terminal (L+,L-) and
CH2 to IC301 pin 4 and GND.
5. Adjust the tuning control (RV303) to receive radio frequency.
6. Check the waveform of the oscilloscope that the CH1 is
demodulated 1kHz signal and CH2 is GND.
7. Connect an AC voltmeter with LPF to speakers terminal (L+,L).
8. Adjust the value of the AC voltmeter to specification by
headphones volume RV302.
Specified values: 155mVrms
9. Connect an AC voltmeter with LPF to speakersterminal
(R+,R-).
10. Measure the value of the AC voltmeter.
11. Check the difference of the L and R to more than 20dB.
12. Input a signal of 1kHz, 316mVrms to transmitter AUDIO IN-A
(R-ch) connector only.
13. Connect an AC voltmeter with LPF to speakers terminal
(R+,R-).
14. Adjust the value of the AC voltmeter to specification by
headphones volume RV302.
Specified values: 155mVrms
15. Connect an AC voltmeter with LPF to speakers terminal
(L+,L-).
16. Measure the value of the AC voltmeter.
17. Check the difference of the L and R to more than 20dB.
Setting :
co
Digital voltmeter
(AC range)
.
+
–
MDR-RF915R/RF945R
9 4 2 8
OSCILLOSCPE
CH1 CH2
IC301 pin4
+ +
– –
OSCILLOSCPE
CH1
IC301 IC301 pin6
33000P pin6
0 5 8 2 9 9 4 2 8
m
OSCILLOSCPE
L+ / R+
CH1 CH2
L+
IC301 pin4
+ +
L– / R–
L–
– –
9 9
CH2
IC301 pin4
+ +
– –
9 9
5