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MDR-RF915R/RF945R
SERVICE MANUAL
HEADPHONES
SPECIFICATIONS
US Model
Canadian Model
MDR-RF915R is the component model block one in the MDR-RF915RK.
MDR-RF945R is the component model block one in the MDR-RF945RK.
9-873-137-12
2001F0200-1
© 2001.6
Sony Corporation
Personal Audio Company
Shinagawa Tec Service Manual Production Group
Ver 1.1 2001. 06
Photo : MDR-RF945R
MDR-RF915RK MDR-RF945RK
Wireless Stereo Headphones MDR-RF915R
MDR-RF945
Transmitter
TMR-RF915R
TMR-RF945
COMPONENT MODEL NAME FOR MDR-RF915RK/
MDR-RF945RK
Headphones
Power source
DC 2.4 V: Built-in rechargeable
battery
Mass Approx.
240 g (8.5 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.


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2
MDR-RF915R/RF945R
SECTION 1
GENERAL
1.
Check the area of your repair for unsoldered or poorly-sol
deredconnections. 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, particularlyt ransis
tors,
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
SAFETY CHECK-OUT
After correcting the original service problem, perform the
following safety checks before releasing the set to the
customer.
5- 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.
MDR-RF945RK
TUNING
button
VOL control
A
A
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.
This section is extracted from
instruction manual.
TABLE OF CONTENTS
Specifications ............................................................................ 1
1. GENERAL ....................................................................... 2
2. DISASSEMBLY
2-1. RX-BASE Board ...................................................... 3
3. ELECTRICAL ADJUSTMENTS .............................. 4
3-1. Free Run Frequency
Check and Adjustment (MRD-RF915R) ....... 5
3-2. Receive Frequency
Check and Adjustment (MRD-RF915R) ....... 5
3-3. Carrier Modulation Check (MRD-RF915R) ............. 5
3-4. Separation Check (MRD-RF915R) ........................... 5
5- Turn up the volume to a moderate
level with the VOL control, then tune
the headphones in to the frequency of
the transmitter with the TUNING
control until you can hear the audio
signal loud and clear.
MDR-RF915RK
Try the above steps 3 and 5 until the
receiving performance becomes better.
TUNING
control
VOL control
B
B
3-5. Free Run Frequency
Check and Adjustment (MRD-RF945R) ......... 6
3-6. Receive Frequency
Check and Adjustment (MRD-RF945R) ......... 6
3-7. Carrier Modulation Check (MRD-RF945R) ............... 6
3-8. Separation Check (MRD-RF945R) ............................. 6
4. DIAGRAMS
4-1. Block Diagrams ........................................................... 8
4-2. Schematic Diagram ..................................................... 9
4-3. Printed Wiring Board ................................................. 10
5. EXPLODED VIEWS........................................................11
6. ELECTRICAL PARTS LIST........................................12


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3
MDR-RF915R/RF945R
SECTION 2
DISASSEMBLY
2-1. RX-BASE BOARD
· This set can be disassembled in the order shown below.
3
Remove the
nine solderings.
9
Remove the two solderings.
RX-BASE board
Solder the each lead wires directly to the position as shown
while being cautions of colors.
Precaution for installtion
Precaution for installtion
7
RX-BASE board
q;
Switch, push (1 key)
Cover (R), hanger
No.203
No.203 (black)
No.202 (red)
No.201 (green)
No.201
No.204
No.205
No.204
No.202
4
Screw (P 2
× 8)
1
Five screws (P 2
× 6)
2
Set the psuh
switch (1 key).
Suspender
1
Slide the suspender in the
direction of the arrow.
6
Button, tuning
(RF945R)
Claw
Claw
2
5
8


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4
MDR-RF915R/RF945R
No.201
Cover (L), hanger
Cover (L), hanger
No.203
No.201, No.203
No.201, No.203
Groove
Set the lead wires
No.204
No.205
No.202
No.202
No.203
No.201
Set the each lead wires as illustrated below.
Cover (R), hanger
A
B
Cover (R), hanger
Groove
Groove
Groove
Groove
Groove
To the driver (030F032).
To the RX-BASE board
Groove
To the driver (030F032).
B
A


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5
MDR-RF915R/RF945R
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-RF915R
Transmitter:TMR-RF915R
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. 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
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.
7. Remove a 33 k
resister between IC301 pin 4 and pin 7.
Setting :
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.
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.
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 :
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 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.
Frequency counter
+
­
IC301 pin4
Setting :
+
­
+
­
IC301 pin6
IC301 pin4
OSCILLOSCPE
CH1
CH2
+
­
Digital voltmeter
(AC range)
LPF
IC301
pin6
33000P
2.2K
+
­
+
­
IC301 pin6
IC301 pin4
OSCILLOSCPE
CH1
CH2
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 :
+
­
Digital voltmeter
(AC range)
L+ / R+
L­ / R­
+
­
+
­
L+
IC301 pin4
OSCILLOSCPE
CH1
CH2
MRD-RF915R
Ver 1.1 2001.06