Sony MDR-RF845R Service manual

MDR-RF845R

SERVICE MANUAL

Ver 1.0 2000. 07

MDR-RF845R is the component model block one in the MDR-RF845RK.

COMPONENT MODEL NAME FOR MDR-RF845RK

Headphones MDR-RF845R Transmitter TMR-RF845R

AEP Model

UK Model

SPECIFICATIONS

Headphones

Power source DC 2.4 V: Built-in rechargeable

Mass Approx. 240 g (8.1 oz.) incl.

built-in rechargeable battery

Built-in Ni-Cd rechargeable battery

Model name NC-AA Voltage 1.2 V Capacity 700 mAh

Design and specifications are subject to change without notice.

battery

HEADPHONES

SECTION 1

GENERAL

This section is extracted from instruction manual.

-A 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.

A MDR-RF845R

TUNING button

VOL control

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.

SAFETY CHECK-OUT

After correcting the original service problem, perform the following safety checks before releasing the set to the customer.

1. Check the area of your repair for unsoldered or poorly-soldered connections. Check the entire board surface for solder splashes and bridges.

2. Check the interboard wiring to ensure that no wires are "pinched" or contact high-wattage resistors.

3. Look for unauthorized replacement parts, particularly transistors, that were installed during a previous repair . Point them out to the customer and recommend their replacement.

4. Look for parts which, through functioning, show obvious signs of deterioration. Point them out to the customer and recommend their replacement.

5. Check the B+ voltage to see it is at the values specified.

6. Flexible Circuit Board Repairing

• Keep the temperature of the 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

— 2 —

SECTION 2

DISASSEMBLY

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

2-1. RX-BASE BOARD

Five screws (P 2

× 6)

Cover (R), hanger

Claw

Precaution for installtion

Slide the suspender in the

direction of the arrow.

Suspender

Set the psuh

switch (1 key).

Switch, push (1 key)

Remove the two solderings.

Button, tuning

RX-BASE board

Remove the

nine solderings.

Claw

Screw (P 2

× 8)

Precaution for installtion

No.205

RX-BASE board

No.204

No.201

No.201 (green)

No.202

No.203

No.203 (black)

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

No.204

No.202 (red)

— 3 —

Set the lead wires

Set the each lead wires as illustrated below.

Cover (L), hanger

Groove

To the driver (030F032).

No.203

No.201

Groove

No.201, No.203

Groove

No.202

Groove

To the RX-BASE board

Cover (R), hanger

No.205

Groove

No.204

To the driver (030F032).

No.201 No.203

No.202

No.201, No.203

Cover (L), hanger

Groove

Cover (R), hanger

— 4 —

SECTION 3

ELECTRICAL ADJUSTMENTS

Notes:

1. Use transmitter with check and adjustment already completed.

2. On adjusting the headphones section, use the transmitter as a jig.

Headphones:MDR-RF845R Transmitter:TMR-RF845R

Procedure:

1. Connect an oscillator with attenuator and terminator (600 Ω) to the transmitter AUDIO IN-A connector (J402).

2. Connect an A C adapter to the transmitter DC IN 9V jack (J404).

3. Short between Q303 corrector and GND on the RX board.

4. Connect a DC supply to TP (R312-C320) and GND on the RX-BASE board.

5. Connect lead wires to IC301 pin 4, pin 6, pin 7 and GND on the RX-BASE board.

6. Connect a resistor 33k Ω between IC301 pin 4 and pin 7.

7. 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 4 or 5 minutes.

2. Check the transmitter power indicator (red) lights.

3. Set the voltage of the DC supply to 1.3V.

4. Connect a frequency counter and an oscilloscope to IC301 pin 4 and GND on the RX-BASE board.

5. Adjust the value of the frequency counter to specification by RV301 on the RX-BASE board.

Specified values: 76kHz ± 50Hz.

6. Open between Q303 corrector and GND on the RX board.

7. When the transmitter off, check the waveform of the oscilloscope as follows:

1.8V

GND

2~3 sec

0.6V

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 INA-L connector only.

4. Set the headphones volume (RV302) to minimum.

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 to CH1 is demodulated 1kHz signal and CH2 is GND.

8. Connect an AC volt meter to IC301 pin 6 and GND.

9. Check the value of the AC volt meter to 26mVrms ± 2mV

3-4. 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 INA-L connector only.

4. Connect an oscilloscope to CH1 is speakers terminal (L+,L-) and CH2 is IC301 pin 4 and GND.

5. Push the headphones tuning switch (S301) to receive radio frequency.

6. Check the waveform of the oscilloscope to CH1 is demodulated 1kHz signal and CH2 is GND.

Connect an A C v olt meter with LPF to speakers terminal (L+,L-).

8. Adjust the value of the AC volt meter to specification by headphones volume RV302.

Specified values: 155mVrms

Connect an A C volt meter with LPF to speak ers terminal (R+,R-).

10. Measure the value of the AC volt meter.

11. Check the difference of the L and R to more than 20dB.

12. Input a signal of 1kHz, 316mVrms to transmitter AUDIO INA-R connector only. Connect an A C volt meter with LPF to speak ers terminal (R+,R-).

13.

14. Adjust the value of the AC volt meter to specification by headphones volume RV302.

Specified values: 155mVrms

15.

Connect an A C v olt meter with LPF to speakers terminal (L+,L-).

16. Measure the value of the AC volt meter.

17. Check the difference of the L and R to more than 20dB.

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 connector only.

4. Keep distance transmitter and headphones to 5 meter over.

5. Set the headphones volume (RV302) to minimum.

6. Set the voltage of the DC supply to 1.2V.

7. Open between Q303 corrector and GND on the RX board.

Connect an oscilloscope CH1 and CH2 to IC301 pin 6 and pin 4.

9. Check the waveform of the oscilloscope to CH1 is demodulated 1kHz signal and CH2 is GND.

10. If CH1 and CH2 are not satisfied step 8, adjust the coil (L301) on the RX board to satisfied step 8.

11. Set the transmitter CHANNEL switch to 1 or 3.

12. Push the headphones tuning switch (S301) to receive radio frequency.

13. Check same step 9.

Adjustment Location : (See page 6)

— 5 —

Adjustment Location :

[RX-BASE BOARD]

(Conductor side)

IC301

GND

Shor

TP(R312-C320)

GND

L–

L+

R–

R+

— 6 —

4-1. BLOCK DIAGRAM

FRONT END

FE UNIT

D301

RECEIVE

FM FE

L301

FREQ.

L302

IC303

D/A

CONV

CF301

CF302

10.7MHz

REG

SECTION 4 DIAGRAMS

FM IF/

1316

DISCRI

OSC

Q301

SWITCH

Q303

AUTO

BLEND

MUTE

IF AMP/DECODE

IC301

PD1

FREE RUN

1/2

COUNTER

VCO

RV301

FREQ.

DECODE

AMP

MONO/ST

DETUNE

MUTE

STEREO

IND

TUNING

IND

RV302

VOLUME

6 2

R-CH

IC304

DETECT

Q305

IC303

TUNING

S301

POWER AMP

IC302

MUTE

Q304

MDR-RF845R

Note on Printed Wiring Board:

• X : parts extracted from the component side.

SPEAKER

L-CH

•

• b : Pattern from the side which enables seeing.

Caution: Pattern face side: Parts on the pattern face side seen from (SideB) the pattern face are indicated. Parts face side: Parts on the parts face side seen from (Side A) the parts face are indicated.

R-CH

SPEAKER

R-CH

Note on Schematic Diagram:

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

• All resistors are in Ω and 1/

•

• A : B+ Line.

• H : adjustment for repair.

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

ON/OFF SW

B+

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

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

• Waveforms are taken with a oscilloscope.

D304

POWER

• Circled numbers refer to waveforms.

• Signal path.

• Signal path. : FM

: Through hole.

less are not indicated except for electrolytics and tantalums.

W or less unless otherwise specified.

: internal component.

from battery terminal.

Voltage variations may be noted due to normal production tolerances.

F:FM L: AUDIO

• IC BLOCK DIAGRAMS

IC302 LA4533M

P/SW

IN1

PRE GND

IN2

REF

SWITCH

BIAS

POWER

IC303 TC7W74FU

MUTE

CIRCIUT

AMP1

AMP2

VCC

CLR

7PR8

RSQ

QDC

GND

MT/SW

OUT1

POWER GND

OUT2

VCC

— 7 — — 8 —

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