Sony MDR-RF975R, TMR-RF975R Service manual

MDR-RF975R

SERVICE MANUAL

Ver 1.1 2001. 06

MDR-RF975R is the component model block one in the MDR-RF975RK.

COMPONENT MODEL NAME FOR MDR-RF975RK

Headphones MDR-RF975R

Transmitter TMR-RF975R

US Model

SPECIFICATIONS

Headphones

Power source DC 2.4 V: Built-in rechargeable

battery

Mass Approx. 350 g (12.3 oz.) incl.

built-in rechargeable battery

Built-in Ni-MH rechargeable battery

Model name NH-AAC Voltage 1.2 V Capacity 1,000 mAh

Design and specifications are subject to change without notice.

9-873-141-12

2001F0200-1

HEADPHONES

Sony Corporation

Personal Audio Company

Shinagawa Tec Service Manual Production Group

MDR-RF975R

SECTION 1

GENERAL

TABLE OF CONTENTS

Specifications ............................................................................ 1

1. GENERAL ......................................................................... 2

2. DISASSEMBLY

2-1. Driver (R Side), RX-BASE Board ........................... 3

2-2. SW Board, Hanger (R) ............................................. 4

2-3. Holder (R) ................................................................. 4

2-4. Driver (L Side) .......................................................... 5

2-5. Hanger (L) ................................................................ 6

2-6. Holder (L) ................................................................. 6

3. ELECTRICAL ADJUSTMENTS

3-1. Free Run Frequency Check and Adjustments........... 7

3-2. Receive Frequency Check and Adjustments ............ 7

3-3. Carrier Modulation Check ........................................ 7

3-4. Expander Output Check ............................................ 7

3-5. Separation Check ...................................................... 7

4. DIAGRAMS

4-1. Block Diagrams .......................................................11

4-2. Schematic Diagram ................................................. 12

4-3. Printed Wiring Board .............................................. 13

5. XPLODEDVIEWS....................................................... 14

This section is extracted from instruction manual.

Turn up the volume to a moderate level with the VOL control. Press the TUNING button briefly for automatic tuning of the headphones. If you do not receive a clear audio signal, press it again.

TUNING button

VOL control

Try the above steps 3 and 5 until the receiving performance becomes better.

6. ELECTRICAL PARTSLIST..................................... 15

Auto power on/off function

When you remove the headphones from your head, the power turns off automatically. Do not allow the self adjusting band to be pulled up, otherwise the headphones will be switched on.

The power turns on.

Flexible Circuit Board Repairing

• Keep the temperature of soldering iron around 270°C during repairing.

• Do not touch the soldering iron on the same conductor of the circuit board (within 3 times).

• Be careful not to apply force on the conductor when soldering or unsoldering.

Notes on chip component replacement

• Never reuse a disconnected chip component.

• Notice that the minus side of a tantalum capacitor may be damaged by heat.

SECTION 2

DISASSEMBLY

• The equipment can be removed using the following procedure .

MDR-RF975R

Set

Driver (R side), RX-BASE board

Driver (L side), Hanger (L)

SW board, Harger (R)

Holder (L)

Note: Follow the disassembly procedure in the numerical order given .

2-1. DRIVER (R SIDE), RX-BASE BOARD

Volume knob

Holder (R)

Set the each leads as illustrated below.

From head band assy (front).

From head band assy (rear).

Groove

From SW board.

Groove

RX-BASE board

Remove the eight solderings.

(Housing (R) side)

Head band assy (front)(natural)

Charge terminal

Remove the

two solderings.

Precaution for installtion

ANT

RX-BASE board

SW board

Head band assy (rear)(natural)

Head band assy (rear)(green)

Driver (natural)

Driver (red)

Holder (R),ear pad

Remove the

two solderings.

Four

claws

Driver

Four screws (M 2

Housing (R)

Precaution for installtion

Plate (R) assy, front

pad, ear

× 5)

Precaution for installtion

Driver (R side)

Head band assy (front)(red)

Solder the each leads directly to the position as shown while being cautions of colors.

SW board

Red Natural

From RX-BASE board.

MDR-RF975R

2-2. SW BOARD, HANGER (R)

Housing (R)

Precaution for installtion

Lid (R), hanger

Remove the

two solderings.

SW board

Holder (R)

Two screw

(P 2

× 8)

Set the each leads as illustrated below.

Groove

From head band assy (front).

From head band assy (rear).

2-3. HOLDER (R)

Spring

(ON/OFF)

From SW board.

Groove

Hanger (R)

Holder (R)

SW board

Cushion assy, head

Band assy (front), Head

Band assy (rear), head

Hanger (R)

Screw (P 2

× 8)

Two screws

× 8)

(P 2

Chassis

2-4. DRIVER (L SIDE)

Set the each leads as illustrated below.

MDR-RF975R

From head band assy (front).

Groove

Housing (L)

Precaution for installtion

Plate (L) assy, front

Pad, ear

Four screws (M 2

Precaution for installtion

× 5)

Driver (L side)

From head band assy (rear).

Driver

Four

claws

Remove the

two solderings.

Two "batterys,

nickle hydrogen"

Ear pad

holder (L)

Green

Natural

Remove the

two solderings.

Green Natural

From head band assy (rear).

MDR-RF975R

2-5. HANGER (L)

Lid (L), hanger

Housing (L)

Precaution for installtion

Two screws

(M 2

× 5)

Holder (L)

Set the each leads as illustrated below.

Hanger (L)

2-6. HOLDER (L)

Groove

From head band assy (front).

From head band assy (rear).

Groove

Hanger (L)

Cushion assy, head

Holder (L)

Band assy (front),head

Band assy

(rear), head

Chassi

Screw (M 2

× 5)

Two screws

(M 1.7

× 3)

SECTION 3

7 7

ELECTRICAL ADJUSTMENTS

MDR-RF975R

Ver 1.1 2001.06

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 Ω) 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 33kΩ 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 33kΩ resistor between IC301 pin 4 and pin 7.

Setting :

Regulated power supply (DC 1.2V)

+ –

Frequency counter

+ –

IC301 pin

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:

1.8V

GND

2-3sec

0.6V

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

IC301 pin6

CH1 CH2

–+–

IC301 pin

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

2.2K

33000P

IC301

pin6

OSCILLOSCPE

IC301 pin6

CH1 CH2

–+–

IC301 pin4

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 pin IC308 pin

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.

MDR-RF975R

Ver 1.1 2001.06

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 25dB.

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 25dB.

Setting :

Digital voltmeter (AC range)

–

LPF

2.2K

33000P

L+ / R+ L– / R–

OSCILLOSCPE

CH1 CH2

L+

–+–

L–

IC301 pin

)

Asjustment Location :

RX-BASE BOARD (Conductor side)

C340

C337

R347

R349

C341

GND

L301: Receive frequency Adjustment

R340

R346

R341

R345

S301

CF301

R342

R344

C320

R343

IC303

C316

C344

R312

D301

L301

C322

C332

C336

C315

C313

D304 power

C321

C309

R325

R308

L302

C314

C355

C312

C329

C331

C317

C319

JC335

D310

C394

C308

C306

IC301

C359

C393

C303

C307

R309

C333

C363

R330

Q304

R322

C302

R320

Q305

IC305

R318

R321

R314

R302

C301

Q303

R348

R354

R331

R363

R364

R361

R360

R332

C323

JC303

10 6

IC302

R333

C361

R304

R310

R362

C362

C381

C304

R334

C352

C343

R353

JC306

C380

C305

R367

C345

JC309

R355

IC301

R305

JC311

Q301

R352

R351

JC304

R358

IC304

R315

C357

R316

C328

C330

C327

IC301

C342

R366

JC336

C326

JC332

GND

C311

RV301

CF302

R350

JC334

R356

C324

R357

C325

JC331

C310

C346

(Connect a 33 KΩ resistor

RV301: Free Run Frequency Adjustment

C318

C347

D303

JC333

L–

L+

R–

R+

MDR-RF975R

Short

+B power line (DC 2.4V)

RV302: Volume control

MDR-RF975R

SECTION 4

DIAGRAMS

Note on schematic diagrams.

Note:

• All capacitors are in µF unless otherwise noted. pF: µµF 50 WV or

less are not indicated except for electrolytics and tantalums.

• All resistors are in Ω and 1/

•

: internal component.

• A : B+ Line.

• H : adjustment for repair.

• Power voltage is dc 2.4V and fed with regulated dc power supply

from battery terminal.

• Voltages are dc with respect to ground under no-signal conditions.

• Voltages are taken with a VOM (Input impedance 10 MΩ).

• Signal path.

F : FM L : AUDIO

• IC BLOCK DIAGRAMS

IC302 LA4533M TP-1

W or less unless otherwise specified.

P/SW

IN1

PRE GND

IN2

REF

SWITCH

BIAS

AMP1

AMP2

POWER

IC305 TC7W74FU (TE12R)

CLR

VCC

RSQ

QDC

3Q2

MUTE

CIRCIUT

GND

MT/SW

OUT1

POWER GND

OUT2

VCC

+ 22 hidden pages