background image
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


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


background image
­ 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.


background image
­ 4 ­
SW BOARD
HANGER COVER (L)
2 screw (P2
× 6)
3 switch support
5 SW board
4 head cushion assy
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)


background image
­ 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
Trans-
mitter
Head-
phones
+
­
+
­
TMR-RF950R
5 m
MDR-RF950
+
­
+
­
oscilloscope
DC voltmeter
[RX-BASE board] ­ Conductor Side ­