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TMR-RF975R
SERVICE MANUAL
TRANSMITTER
SPECIFICATIONS
US Model
TMR-RF975R is the component model block one in the MDR-RF975RK.
9-873-140-12
2001F0200-1
© 2001.6
Sony Corporation
Personal Audio Company
Shinagawa Tec Service Manual Production Group
Ver 1.1 2001. 06
Headphones
MDR-RF975R
Transmitter
TMR-RF975R
COMPONENT MODEL NAME FOR MDR-RF975RK
General
Carrier frequency
913.5 ­ 914.5 MHz
Channel
Ch1, Ch2, Ch3
Modulation
FM stereo
Frequency response
18 ­ 22,000 Hz
Transmitter TMR-RF975R
Power source
DC 9 V: supplied AC power adaptor
Audio input
phono jacks/stereo mini jack
Dimensions
Approx. 130
135 150 mm
(5 1/4 5 3/8 6 in.) (w/h/d)
Mass
Approx. 200 g (7 oz.)
Design and specifications are subject to change without
notice.
XX
XX


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2
TMR-RF975R
SECTION 1
GENERAL
This section is extracted from
instruction manual.
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.
Setting up the
transmitter
1 Connect the transmitter to audio/video
equipment. Select one of the hookups
below depending on the jack type:
To connect to a headphones jack
DC IN 9V
OFF ON
FILTER
NOISE
12 3
CHANNEL
R
BA
L
AUDIO IN
Transmitter
Left channel
(white)
Right channel
(red)
Unimatch plug
adaptor
(supplied)
Discman, MD,
WALKMAN*, VCR,
etc.
to headphones
jack (stereo
mini jack)
Connecting cord
(supplied)
to AUDIO IN
A jacks
to headphones
jack (stereo
phone jack)
A
TABLE OF CONTENTS
Specifications ............................................................................ 1
1. GENERAL ....................................................................... 2
2. DISASSEMBLY
2-1. Housing (Upper) ....................................................... 3
2-2. TX-BASE Board ....................................................... 3
3. ELECTRICAL ADJUSTMENTS ............................. 4
4. DIAGRAMS
4-1. Block Diagrams ........................................................ 5
4-2. Schematic Diagram­ TX-BASE Section ­ ............... 6
4-3. Printed Wiring Board ­ TX-BASE Section ­ .......... 7
4-4. Schematic Diagram
­ BATTERY CHARGER Section ­ .......................... 8
4-5. Printed Wiring Board
­ BATTERY CHARGER Section ­ .......................... 9
5. EXPLODED VIEWS....................................................10
6. ELECTRICAL PARTS LIST.....................................11


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3
TMR-RF975R
SECTION 2
DISASSEMBLY
2-1. HOUSING (UPPER)
Note: Follow the disassembly procedure in the numerical order given .
1
Four screws (P 2
× 8)
Housing (upper)
2
2-2. TX-BASE BOARD
3
TX-BASE board
2
1
Screw (P 2
× 6)
Screw
Housing (upper)
2-3. CHG-NR BOARD
Housing (upper)
2
CHG-NR board
1
Four screws (P 2
× 6)


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4
TMR-RF975R
SECTION 3
ELECTRICAL ADJUSTMENTS
Transmission Frequency Check
1. Set the noise filter SW to OFF.
2. Input a signal of 1 kHz, 40 mVrms to only the L-CH (J402).
3. Connect a telescopic antenna to the frequency counter input
and extend the antenna to a length of approximately 8 cm.
4. Place TX-BASE board close to the frequency counter, then
measure the frequencies of CH1, CH2 and CH3 and make
sure the values are as follows:
CH1 : 913.5 MHz
± 200 kHz
CH2 : 914.0 MHz
± 200 kHz
CH3 : 914.5 MHz
± 200 kHz
When the frequency does not satisfy the specified value,
set the channel switch (S402) to CH2, then adjust the value of
the frequency counter to 914.0 MHz by trimmer capacitor in
the VCO unit.
Standard value :913.9MHz to 914.1MHz.
When completed with replacement, recheck the frequecies of
CH1, CH2 and CH3.
Compresser Output Check
1. Set the channel to CH2.
2. Input a signal of 1 kHz, 316 mVrms to L-CH and R-CH of
J402.
3. Measure IC 601 pin 7 and IC 602 pin 7 on the CHG-NR
board using a digital voltmeter (AC range) and put down a
value mesured. (Fig.1).
4. Input a signal of 1 kHz, 31.6 mVrms to L-CH and R-CH of
J402.
5.
Measure IC 601 pin 7 and IC 602 pin 7 on the CHG-NR
board using a digital voltmeter (AC range) and put down a
value mesured (Fig.1).
Confirm that there is a difference of step 3 and 5 by 10dB
±
3dB.
6. When the frequency is not satisfied the specified value,
exchange TX- BASE board or CHG-NR board.
Setting :
Pilot Signal and MPX Signal Modulation Check and
Adjustment
1. Set the channel to CH2.
2. An electric wave is output for 5 or 10 minutes when OFF to ON
a power supply with no signal input (Power indicator will ON).
3. Set the RV402 and RV403 to max. (clockwise)
4. Connect a digital voltmeter (AC range) to the center terminal
of RV403 (Fig.2).
5. Adjust the value of the digital voltmeter to minimum by RV401.
6. See the RV402 to minimum. (counter clock wise)
7. Adjust the value of the digital voltmeter to max by L407.
8. Adjust the value of the digital voltmerter to 2.1to 2.6mVrms
by RV403.
9. Connect a digital voltmeter (AC range) with LPF to movable
terminal of RV403 (Fig.2).
10. Input a signal of 1 kHz, 316 mVrms to only the L-CH.
11. Adjust the value of the digital voltmeter to 5.2 to 6.4 mVrms
by RV402.
Connection points and Adjustment Location :
AF signal
generator
Telescopic
antenna
8 cm
L-CH / R-CH (J402)
TMR-RF975R
set
TMR-RF975R
set
Frequency counter
S402
J402
(L-CH) (R-CH)
CH3
CH2 CH1
VCO
UNIT
RV403
RV402
RV401
Hole
Sheet
L407
R464
IC 602
IC 601
1
8
4
5
1
8
4
5
CHG-NR board
+
­
digital
voltmeter
(AC range)
(Fig. 1)
7 pin
RV401-403,
L407
Modulation
check and
adjustment.
Trimmer capacitor:
Transmission
frequency
adjustment
+
­
digital
voltmeter
(AC range)
(Fig. 2)
R464


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TMR-RF975R
5
5
4-1. BLOCK DIAGRAMS
J401
S401
NOISE FILTER
NOISE
FILTER
CH1
AMP
BUFFER
BUFFER
Q401
RECT
D404,405
CHANNEL
SET
Q408
2V
D408
INPUT
DET
DIVIDER
BUFFER
OSC
AMP
TIME
DEVISION
MPX
AUDIO IN
B
J402
A
OFF
|
ON
S402
CHANNEL
L
R
R-CH
R-CH
R-CH
14
12
11
9
8
10
7
6
CH2
AMP
1
X401
38kHz
RV402
RV401
L407
RV403
MOD IN
VS
IC401
IC601
(L-CH)
IC602
(R-CH)
Q403
LPF
IC403
STEREO MPX
Q402,405
+5V
REG
SWITCH
Q404
POWER
ON/OFF
Q406,407
SWITCH
Q601
SWITCH
Q602
SWITCH
Q604
SWITCH
Q603
OSC
Q605
REF V
IC604(2/2)
DETECT
IC402
+5V
REG
IC605
COMPARATOR
IC603
DETECT
IC604(1/2)
ANT
5V
ANT401
D401
D402
CHARGE
TERMINAL
(TO MDR-RF975R)
power
chg
1
2
3
VCO401
(VCO UNIT)
MODULATION
MODULATION
MODU-
LATION
MODULATION
MODULATION
7
2
1
13
CHG-NR BOARD
TX-BASE BOARD
(1/2)
CHG-NR BOARD (2/2)
I
O
V
B+
5V
D407
+
­
J404
DC IN 9V
· R-ch is omitted due to same as L-ch.
· Signal path.
L
: AUDIO
F
: FM
SECTION 4
DIAGRAMS