SONY MDRRF975R
Manual de Servicio

SECTION 3 ELECTRICAL ADJUSTMENTS
Notes: 1. Use transmitter with check and adjustment alreadycompleted. 2. On adjusting the headphones section, use the transmitter as a jig. Headphones:MDR-RF975R Transmitter:TMR-RF975R Procedure: 1. Connect an oscillator with attenuator and terminator (600 �) to the transmitter AUDIO IN-A connector (J402). 2. Connect an AC adapter to the transmitter DC IN 9V jack (J404). 3. Short between Q303 collector and GND on the RX board. 4. Connect DC 2.4V to the +B power line externally. 5. Connect lead wires to IC301 pin 4, pin 6, pin 7, IC 307 pin 7, IC 308 pin 7 and GND on the RX-BASE board. 6. Connect a 33k� resistor between IC301 pin 4 and pin 7. 7. Connect lead wires to the speakers� terminals (L+,L-,R+,R-) on the RX-BASE board. (See page 9) 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 the confirmation for less than 5 minutes. 2. Check the transmitter power indicator (red) lights. 3. Set the transmitter CHANNEL switch to 1. 4. Connect DC 1.2V across TP and GND. 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. 7. Remove a 33k� resistor between IC301 pin 4 and pin 7. Setting :
Regulated power supply (DC 1.2V)
+ �

MDR-RF975R
Ver 1.1 2001.06

12. Set the transmitter CHANNEL switch to 1. 13. Push the headphones tuning switch (S301) to receive radio frequency. 14. Check same step 8. 15. Set the transmitter CHANNEL switch to 3. 16. Push the headphones tuning switch (S301) to receive radio frequency. 17. Check same step 8. Setting :
Regulated power supply (DC 1.2V) OSCILLOSCPE

+ �

TP

IC301 pin6

CH1

CH2 ++ ��

IC301 pin4

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. Push the headphones tuning switch (S301) 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 40mVrms ± 5mV Setting :
Digital voltmeter (AC range) LPF OSCILLOSCPE

Frequency counter

+ �

2.2K 33000P

IC301 IC301 pin6 pin6

CH1

++ ��

CH2

IC301 pin4

TP

+ �

IC301 pin4

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 INA(L-ch) connector only. 4. Keep distance between transmitter and headphones to 5 meters over. 5. Set the headphones volume (RV302) to minimum. 6. Connect DC 1.2V across TP and GND. 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. Open between Q303 corrector and GND on the RX board. 11. When the transmitter off, check the waveform of the oscilloscope as follows:

3-4. Expander Output Check 1. Set the transmitter CHANNEL switch to 2. 2. Input a signal of 1kHz, 316mVrms to transmitter AUDIO IN-A L and R connector. 3. Connect an AC voltmeter to IC307 pin 7 and IC308 pin 7. 4. Measure the value of the AC voltmeter. 5. Input a signal of 1kHz, 31.6mVrms to transmitter AUDIO INA L and R connector. 6. Measure the value of the AC voltmeter. 7. Check the difference of the step 4 and step 6 to more than 20 dB ± 3 dB. Setting :
Digital voltmeter (AC range)
+ �

IC307 pin7 IC308 pin7

1.8V

2-3sec GND

0.6V

3-5. Separation 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. Connect an oscilloscope CH1 to speakers terminal (L+,L-) and CH2 to IC301 pin 4 and GND. 5. Push the headphones tuning switch (S301) receive radio frequency.

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