Sony NC-AA MDR-RF950 User manual

MICROFILM
SERVICE MANUAL
WIRELESS STEREO HEADPHONES
US Model
Canadian Model
SPECIFICATIONS
MDR-RF950
MDR-RF950 is headphones
in MDR-RF950RK. TABLE OF CONTENTS
1. GENERAL ................................................................. 2
2. DISASSEMBLY ......................................................... 3
3. ELECTRICAL ADJUSTMENTS
3-1. Checking/Adjusting Receiving Frequency..................... 5
3-2. Checking/Adjusting Degree of Modulation
of Main Carrier (L + R) .................................................. 6
3-3. Checking/Adjusting Separation ...................................... 7
4. DIAGRAMS
4-1. Printed Wiring Boards..................................................... 11
4-2. Schematic Diagram ......................................................... 13
5. EXPLODED VIEWS................................................ 15
6. ELECTRICAL PARTS LIST ............................... 17
Notes on chip component replacement
• Never reuse a disconnected chip component.
• Notice that the minus side of a tantalum capacitor may be dam-
aged by heat.
Ver 1.0 1998. 06

– 2 –
SECTION 1
GENERAL
This section is extracted from
instruction manual.

– 3 –
FRONT PLATE ASSY
RX-BASE BOARD
Note: Follow the disassembly procedure in the numerical order given.
SECTION 2
DISASSEMBLY
• This set can be disassembled in the order shown below.
SET FRONT PLATE ASSY RX-BASE BOARD SW BOARD
HANGER COVER (L)
4 Remove two solders
of driver lead.
1 ear pad
3 front plate assy
2 three screws
(P2
× 6)
2 hanger cover (R)
4 RX-BASE board
3 Remove four solders
of leads.
1 two screws
(P2
× 6)
1 two screws
(P2
× 10)
3 Remove three solders
of leads.

– 4 –
SW BOARD
HANGER COVER (L)
2 screw (P2 × 6)
3 switch support
5 SW board
4 head cushion ass
y
1 two head bands
2 hanger cover (L
)
3 Remove two solders
of battery lead.
1 two screws
(P2
× 6)
1 two screws
(P2
× 10)

– 5 –
Note:
1. The adjustments should be performed in the order given.
2. The transmitter (TMR-RF950R) already checked and adjusted should be used.
3-1. Receiving Frequency Check and Adjustment
Preparation:
Procedure:
1. Set the channel of the transmitter to CH2.
2. Turn OFF the noise filter switch on the transmitter.
3. Enter 1 kHz 316 mVrms signal only to the Lch on the transmitter.
4. Place the transmitter away from the headphone (MDR-RF950) more than 5 m.
5. Set the volume control (RV301) on the RX-BASE board to the minimum position.
6. Set the tuning control (RV302) on the RX-BASE board to the center position.
7. Connect a DC voltmeter and an oscilloscope between IC301 pin @¡ and ground on the RX-BASE board.
8. After confirming that demodulated 1 kHz waveform (about 13 mV) appears on the oscilloscope, check that the DC voltmeter indicates
DC1 V to 1.2 V.
9. If demodulated 1 kHz waveform does not appear on the oscilloscope, or if the voltage is out of the specified value, adjust the air-core
coil (L301) on the RX-BASE board so that the demodulated 1 kHz waveform appears on the oscilloscope, and under this condition,
adjust finely the air-core coil (L301) so that the DC voltmeter indicates DC1.1 V.
10. Finally, check that signals are received when the channel is changed over to CH1/CH3 on the transmitter, then when the tuning control
(RV302) on the RX-BASE board is rotated.
Adjustment Location: RX-BASE board (See page 9.)
SECTION 3
ELECTRICAL ADJUSTMENTS
AF OSC
ATT
AUDIO IN (Lch)
1 kHz 316 mVrms
600 Ω
Trans-
mitter Head-
phones
+
–+
–
TMR-RF950R 5 m MDR-RF950
+
–
+
–
oscilloscope
DC voltmeter
[RX-BASE board] – Conductor Side –

– 6 –
3-2. Degree of Modulation of Main Carrier (L + R) Check and Adjustment
Preparation:
Procedure:
1. Set the channel of the transmitter to CH2.
2. Turn OFF the noise filter switch on the transmitter.
3. Enter 1 kHz 316 mVrms signal only to the Lch on the transmitter.
4. Set the volume control (RV301) on the RX-BASE board to the minimum position.
5. Connect an AC voltmeter and an oscilloscope between IC 301 pin @¡ and ground on the RX-BASE board.
6. Rotating the tuning control (RV302) on the RX-BASE board, receive signals.
7. After confirming that demodulated 1 kHz waveform appears on the oscilloscope, check that the AC voltmeter indicates 12 mVrms to
15 mVrms.
8. If out of the specified value, rotate RV404 on the TX-BASE board in the transmitter (TMR-RF950R) so as to attain 13.5 mVrms.
Adjustment Location: TX-BASE board in the transmitter (TMR-RF950R) (See page 8.)
AF OSC
ATT
AUDIO IN (Lch)
1 kHz 316 mVrms
600 Ω
Trans-
mitter Head-
phones
+
–+
–
TMR-RF950R MDR-RF950
+
–
+
–
oscilloscope
AC voltmeter
[RX-BASE board] – Conductor Side –

– 7 –
3-3. Separation Check and Adjustment
Preparation:
Procedure:
1. Set the channel of the transmitter to CH2.
2. Turn OFF the noise filter switch on the transmitter.
3. Enter 1 kHz 316 mVrms signal only to the Lch on the transmitter.
4. Connect an AC voltmeter and an oscilloscope to the Lch speaker output (both ends of MDD01) on the RX-BASE board.
5. Rotating the tuning control (RV302) on the RX-BASE board, receive signals.
6. Adjust the volume control (RV301) on the RX-BASE board so that the Lch speaker output (both ends of MDD01) on the RX-BASE
board becomes 155 mVrms.
7. Connect an AC voltmeter and oscilloscope to the Rch speaker output (both ends of MDD02) and measure voltage.
8. Check that a difference in speaker output level between Lch and Rch (i. e., separation) is over 20 dB. If not over 20 dB, rotate RV303
on the RX-BASE board to minimize the Rch output, then reconfirm that a difference in speaker output level between Lch and Rch is
over 20 dB.
9. Enter 1kHz 316 mVrms signal only to the Rch on the transmitter.
10. Adjust the volume control (RV301) on the RX-BASE board so that the Rch speaker output (voltage across MDD02) on the RX-BASE
board become 155 mVrms.
11. Connect an AC voltmeter and oscilloscope to the Lch speaker output (both ends of MDD01) and measure voltage.
12. Check that a difference in speaker output level between Lch and Rch (i.e., separation) is over 20 dB.
Adjustment Location: RX-BASE board (See page 9.)
+
–
oscilloscope
AC voltmeter
[RX-BASE board] – Conductor Side –
AF OSC
ATT
AUDIO IN (Lch or Rch)
1 kHz 316 mVrms
600 Ω
Trans-
mitter Head-
phones
+
–+
–
TMR-RF950R MDR-RF950
+
–

– 8 –
Adjustment Location:
Transmitter (TMR-RF950R)
RV404
Degree of
Modulation of
Main Carrier (L + R)
Adjustment
NOISE FILTER
OFF
˜
ON
J402
(Rch) J403
(Lch)
S402
CHANNEL
CH1
˜
CH2
˜
CH3
S401
[TX-BASE board] – Component Side –

– 9 – – 10 –
SECTION 4
DIAGRAMS
Headphone (MDR-RF950)
L301
Receiving Frequency
Adjustment
RV301
VOL
RV302
TUNING
MAX
MIN
[RX-BASE board] – Component Side –
IC301
RV303
Separation Adjustment
[RX-BASE board] – Conductor Side –
POWER
SWITCH MUTE
BIAS
AMP
AMP
1
2
3
4
5 6
7
8
9
10 MUTE
R-OUT
GND
L-OUT
VCC
PWR
R-IN
GND
L-IN
REG
• IC Block Diagrams
IC301 CXA1611N-T4
IC302 LA4533M