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SERVICE MANUAL
COMPACT DISC CHANGER
SPECIFICATIONS
CDX-757MX
Model Name Using Similar Mechanism
CDX-747X
CD Drive Mechanism Type
MG-251B-137
Optical Pick-up Name
KSS-720A
US Model
Canadian Model
E Model
System
Compact disc digital audio system
Laser diode properties Material: GaAlAs
Wavelength: 780 nm
Emission Duration: Continuous
Laser out-put Power: Less than
44.6
µW*
* This output is the value measured at a distance of 200 mm
from the objective lens surface on the Optical Pick-up Block.
Frequency response
5 ­ 20,000 Hz
Wow and flutter
Below the measurable limit
Signal-to-noise ratio
102 dB
Outputs
BUS control output (8 pins)
Analog audio output (RCA pin)
Current drain
800 mA (during CD playback)
800 mA (during loading or ejecting
a disc)
Operating temperature ­10
°C to +55°C (14°F to 131°F)
Dimensions
Approx. 262
× 90 × 185 mm
(10 3/8
× 3 5/8 × 7 3/8 in.)
(w/h/d) not incl. projecting parts
and controls
Mass
Approx. 2.1 kg (4 lb. 10 oz.)
Power requirement
12 V DC car battery
(negative ground)
Supplied accessories
Disc magazine (1)
Parts for installation and
connections (1 set)
Design and specifications are subject to change without
notice.
Ver 1.1 2002.08
9-873-618-02
Sony Corporation
2002H0500-1
e Vehicle Company
C
2002.08
Published by Sony Engineering Corporation


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2
CDX-757MX
SAFETY-RELATED COMPONENT WARNING!!
COMPONENTS IDENTIFIED BY MARK 0 OR DOTTED
LINE WITH MARK 0 ON THE SCHEMATIC DIAGRAMS
AND IN THE PARTS LIST ARE CRITICAL TO SAFE
OPERATION. REPLACE THESE COMPONENTS WITH
SONY PARTS WHOSE PART NUMBERS APPEAR AS
SHOWN IN THIS MANUAL OR IN SUPPLEMENTS PUB-
LISHED BY SONY.
ATTENTION AU COMPOSANT AYANT RAPPORT
À LA SÉCURITÉ!
LES COMPOSANTS IDENTIFIÉS PAR UNE MARQUE 0
SUR LES DIAGRAMMES SCHÉMATIQUES ET LA LISTE
DES PIÈCES SONT CRITIQUES POUR LA SÉCURITÉ
DE FONCTIONNEMENT. NE REMPLACER CES COM-
POSANTS QUE PAR DES PIÈCES SONY DONT LES
NUMÉROS SONT DONNÉS DANS CE MANUEL OU
DANS LES SUPPLÉMENTS PUBLIÉS PAR SONY.
Flexible Circuit Board Repairing
·Keep the temperature of the soldering iron around 270 °C dur-
ing 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 dam-
aged by heat.
CAUTION
Use of controls or adjustments or performance of procedures
other than those specified herein may result in hazardous ra-
diation exposure.
SERVICING NOTES
NOTES ON HANDLING THE OPTICAL PICK-
UP BLOCK OR BASE UNIT
The laser diode in the optical pick-up block may suffer electro-
static breakdown because of the potential difference generated by
the charged electrostatic load, etc. on clothing and the human body.
During repair, pay attention to electrostatic breakdown and also
use the procedure in the printed matter which is included in the
repair parts.
The flexible board is easily damaged and should be handled with
care.
NOTES ON LASER DIODE EMISSION CHECK
The laser beam on this model is concentrated so as to be focused
on the disc reflective surface by the objective lens in the optical
pick-up block. Therefore, when checking the laser diode emis-
sion, observe from more than 30 cm away from the objective lens.
US/Canadian model:
If the optical pick-up block is defective, please replace the whole
optical pick-up block.
Never turn the semi-fixed resistor located at the side of optical
pick-up block.
DISC MAGAZINE GETTING OUT PROCEDURE
ON THE POWER SUPPLY IS OFF
Remove the CASE (LOWER. T) beforehand
1) Press the lever (ML.S) assy in the direction of arrow A.
2) Removal the magazine assy.
Note: Take out the magazine only when the tray is completely within the
magazine. If the disk or tray is sticking out, turn on the power and
eject the magazine.
Lever (ML.S)
Magazine assy
A
OPTICAL
PICK-UP
BLOCK
SEMI-FIXED
RESISTOR


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3
CDX-757MX
TEST DISC
This set can playback a CD-R, CD-RW for audio use. When test
this set, use the following test disc.
Test disc for CD-R: TCD-R082LMT (Part No.: J-2502-063-1)
Test disc for CD-RW: TCD-W082L (Part No.: J-2502-063-2)
Notes on CD-R/CD-RW discs
· You can play CD-Rs/CD-RWs (recordable CDs/rewritable CDs) on
this unit (fig. E).
· Some CD-Rs/CD-RWs (depending on the equipment used for its
recording or the condition of the disc) may not play on this unit.
· You cannot play a CD-R/CD-RW that is not finalized*.
· A CD-R/CD-RW to which a session can be added can be played.
* A process necessary for a recorded CD-R/CD-RW disc to be played
on the audio CD player.
E
Audio CD
MP3 files
1
2
6
3
5
7
1
2
6
7
4
8
3
5
8
4
9
About MP3 files
Tree 1
Tree 2
Tree 3
Tree 4
Tree 5
(root)
Folder (album)
MP3 file (track)
MP3 (MPEG 1 Audio Layer-3) is a standard technology and format for
compressing a sound sequence. The file is compressed to about 1/10 of its
original size. Sounds outside the range of human hearing are compressed
while the sounds we can hear are not compressed.
Notes on discs
You can play MP3 files recorded on CD-ROMs, CD-Rs (recordable CDs),
and CD-RWs (rewritable CDs). The disc must be in the ISO 9660*1 level 1 or
level 2 format, or Joliet or Romeo in the expansion format. You can use a
disc recorded in Multi Session*2.
*1 ISO 9660 Format
The most common international standard for the logical format of files
and folders on a CD-ROM.
There are several specification levels. In Level 1, file names must be in
the 8.3 format (no more than eight characters in the name, no more than
three characters in the extension ".MP3") and in capital letters. Folder
names can be no longer than eight characters. There can be no more
than eight nested folder levels.
In level 2, file names can be up to 31 characters long (including the
delimiter, the dot ".", and the extension ". MP3"). Each folder can have
up to 8 trees.
For Joliet or Romeo in the expansion format, make sure of the contents
of the writing software, etc.
*2 Multi Session
This is a recording method that enables adding of data using the Track-
At-Once method. Conventional CDs begin at a CD control area called
the Lead-in and end at an area called Lead-out. A Multi Session CD is a
CD having multiple sessions, with each segment from Lead-in to Lead-
out regarded as a single session.
CD-Extra: A format that contains audio tracks (audio CD data) in
Session 1, and a data track in Session 2.
Mixed CD: A format that contains a data track and audio tracks (audio
CD data) in a session.
Notes
· If MP3 files and Audio data are mixed in a disc, the first identified
file or data will be played back.
· With formats other than ISO 9660 level 1, folder names or file
names may not be displayed correctly.
· When naming, be sure to add the file extension ".MP3" to the file
name.
· If you put the extension ".MP3" to a file other than MP3, the unit
cannot recognize the file properly and will generate random noise
that could damage your speakers.
The playback order of the MP3 files
The playback order of the folders and files is shown in the illustration
above.
Notes
·A folder that does not include an MP3 file is skipped.
·If you playback an MP3 file before the information on all the CDs
in the disc magazine has been read, and then set the ignition to
OFF or select another source, the beginning of the current track
may play back when you resume playback.
· The unit reads the disc information (the number of folders and
files, or the location of the data) before playback of an MP3 file. It
may take more time to start playback of a disc with a complex file
structure.
·When a disc magazine is inserted into the CD changer or the reset
button of the connected car audio is pressed, the unit will
automatically be activated and read the information on the CDs.
When the information on all the CDs in the disc magazine has
been read, the unit will automatically stop operation. The unit
firstly reads all of the disc information in the disc magazine.
Depending on the recording method, it may take some time to
stop the operation even if you set the ignition key to OFF during
disc reading. This is not a malfunction.
· The following discs take a longer time to start playback.
­a disc recorded with complicated tree structure.
­a disc recorded in Multi Session.
­a disc to which data can be added.
We recommend that you make only one or two trees for each disc.
· Depending on the condition of the disc, it may not play back. For
details, please refer to "Notes on discs."
·Maximum folder number in a disc: 255* (including root folder and
empty folders)
·Maximum file number in a disc: 511*
*
Maximum number of files and folders: 512
When a file/folder name contains many characters, this number
may become less than 512.
Cautions when playing a disc that is recorded in Multi Session
· When the first track of the first session is audio CD data: Non-music data
information (track number, time, etc.) is displayed with no sound.
· When the first track of the first session is not audio CD data:
­ Audio CD data is played back normally; other data is played back with
no sound. (MP3 file(s) cannot be played back.)
­ If no MP3 file is in the disc, "NO Music" is displayed and nothing is
played back. (Audio CD data is not recognized.)
Note on character codes
Character codes vary depending on the master unit.
For details, refer to the operating instructions for the master unit.
Note on display of playing time
In the following cases, elapsed playing time may not be displayed
accurately.
­ when an MP3 file of VBR (variable bit rate) is played.
­ during fast-forward/reverse.
Tip
· To specify a desired playback order, before the folder or file
name, input the order by number (e.g., "01," "02"), then record
contents onto a disc. (The order differs depending on the writing
software.)
·A disc/album/track name or track number that is over 99 may not
be displayed accurately when this unit is connected to a master
unit that does not support MP3. A master unit that supports MP3
is recommended.
About ID3 tag version 2
Although not a malfunction, the following occurs when
an MP3 file containing ID3 tag ver.2 is played:
­ When skipping a portion of ID3 tag ver.2 (at the
beginning of the track), sound is not output.
Skip time changes depending ID3 tag ver.2 capacity.
Example: At 64 kbytes, it is about 2 seconds
(with RealJukebox).
­ The displayed elapsed playing time when skipping a
portion of ID3 tag ver.2 is inaccurate.
For MP3 files of a bit rate other than 128 kbps, time is
not displayed accurately during playback.
­ When an MP3 file is created with MP3 conversion
software (ex. RealJukebox*), ID3 tag ver.2 will
automatically be written.
* "RealJukebox is a registered trademark of
RealNetworks, Inc."
As of December, 2001


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4
CDX-757MX
Q1
What is MP3?
MP3 (MPEG Audio Layer3) is a standard
for compressing audio parts of Moving
Pictures Experts Group (MPEG).
The special feature of MP3 is that the music
data is compressed to about 1/10 of its
original size while retaining the same
sound quality as a CD or an MD.
Compared with an audio disc (maximum
74 minutes running time), MP3 lets you
compress about 10 audio discs or 160 four-
minute songs into a CD-R/RW of 650MB.
Note
Recorded music is limited to private use only. Use
of music beyond this limit requires the permission
of the copyright holders. Copyright law prohibits
copying, distributing, or delivering all or part of
the contents.
Q2
What kind of MP3 files can be
played back?
MP3 files in CD-ROMs, CD-Rs, and CD-
RWs can be played.
Pay attention to the following points when
creating MP3 data CDs using your
computer, CD-R/RW drive, writing
software, or MP3 file.
· The file must be in the ISO 9660 level 1 or
level 2 format, or Joliet or Romeo in the
ISO 9660 expansion format.
A folder name or a file name with the
format other than ISO 9660 level 1 may
not be displayed correctly. When
creating MP3 data CDs, the format of ISO
9660 level 1 is recommended.
· When naming, be sure to add the file
extension ".MP3" to the MP3 file name.
The unit cannot recognize an MP3 file
without the extension ".MP3," or a file
that is not MP3 format, even with the
extension ".MP3."
Q3
Is there maximum number of
folders or files to play?
Pay attention to the maximum numbers
mentioned below.
·Maximum folder number in a disc: 255*
(including root folder and empty folders)
·Maximum file number in a disc: 511*
*
Maximum number of files and folders:
512
When a file/folder name contains
many characters, this number may
become less than 512.
· The maximum number of trees which
can be played is 8.
The unit allows you to change the folders,
to play just the files in your favorite folder
repeatedly, or to play files randomly, create
folders according to artist name or album,
and put related MP3 files into folders to use
the unit as a CD changer.
Q4
Can the unit play a data CD with
folder levels?
The unit can play a data CD with folder
levels.
Q5
Is there any restriction about the
bit rate regarding playback of
MP3 files?
There is no specific restriction, but a bit rate
of more than 128kbps is recommended
from the perspective of sound quality. The
unit also supports VBR (Variable Bit Rate).
Note
Elapsed playing time may not be displayed
accurately during cue/reverse.
Q6
Does the unit support a disk of
80 minutes running time (700
MB data capacity)?
The unit supports a disk of 80 minutes
running time (700 MB data capacity).
Q7
Can the unit play a CD-R/RW
containing both music CD data
(CD-DA) and MP3 file data?
The first identified file or data will be
played back.
Q8
Can the unit play a disc to which
data can be added (non-finalized
disc)?
The unit can play a non-finalized disc.
Q9
Can the unit play a Multi Session
disc?
The unit can play a Multi Session disc. For
details, refer to the operating instructions.
Q10 Does the unit support Emphasis?
The unit does not support Emphasis.
Q11 What is the sampling rate
supporting the unit?
The unit is supported from 16kHz to
48kHZ.
Q12 Does the unit support the play
list of m3u?
The unit does not support the play list of
m3u.
Q13 Does the unit support ID3-Tag?
The unit supports ID3 tag ver.1.
Pay attention to the following points about
ID3 tag ver.2.
Q14 Is a file name/a folder name of
MP3 different from the name
when creating a data CD (the
name displayed on your
computer)?
On this unit, a file name/a folder name is
displayed as below.
·A file name/a folder name can be
displayed up to 8 characters.
A 9th or later character cannot be
displayed or scrolled.
·A folder name or a file name in a format
other than ISO 9660 level 1 may not be
displayed correctly. The file name should
only use one byte uppercase, one byte
numeric characters, or an underscore
("__"). It should also be no more than 8
characters long, and with no more than
three characters in the extension.
· Japanese phonetic symbols/ Chinese
characters cannot be displayed.
Only one byte uppercase (A-Z), one byte
numeric character (0-9), and one byte
symbol ("_", ".", "<", ">", "/", "+", "*")
can be displayed. One byte lowercase (a-
z) is changed to an uppercase character,
and any other characters are displayed as
"*".
Q15 MP3 files recorded onto a CD-R/
RW cannot be played.
This may happen in following cases.
· The recording method onto CD-R/RW is
the packet write method.
· The extension file is not an ".MP3."
· The file data is not MP3 format.
· Some recording condition (omission of
data, etc.) or some disc condition (dirt,
crack, curving, etc.) may cause inability
to playback an MP3 file.
Q16 It takes some time to start
playback of MP3 file.
The unit reads the disc information (the
number of folders and files, or the location
of the data) before playback of MP3 file. It
may take more time to start playback of a
disc with many trees.
Please refer to the instruction manual for
details.
Q17 Playback skipping and no
playback occur.
Recording condition onto CD-R/RW
(omission of data, etc.) or disc condition
(dirt, crack, curving, etc.) may cause
playback skipping or no playback.
Q18 Can WAVE files be played back
on this unit?
WAVE files cannot be played back on this
unit.
Q19 Can other compressed formats,
such as ATRAC3, be played back
on the unit?
Only MP3 can be played back on the unit.
MPEG1
48kHz
44.1kHz
32kHz
MPEG2
24kHz
22.05kHz
16kHz
About ID3 tag version 2
Although not a malfunction, the following occurs
when an MP3 file containing ID3 tag ver.2 is
played:
­When skipping a portion of ID3 tag ver.2 (at the
beginning of the track), sound is not output. Skip
time changes depending ID3 tag ver.2 capacity.
Example: At 64 kbytes, it is about 2 seconds
(with RealJukebox).
­ The displayed elapsed playing time when skipping
a portion of ID3 tag ver.2 is inaccurate.
For MP3 files of a bit rate other than 128 kbps, time
is not displayed accurately during playback.
­ When an MP3 file is created with MP3 conversion
software (ex. RealJukebox*), ID3 tag ver.2 will
automatically be written.
*
"RealJukebox is a registered trademark of
RealNetworks, Inc."
As of December, 2001
011TRACK.MP3
020TRACK.MP3
091TRACK.MP3
100TRACK.MP3
ROOT
01_
ALBUM
02_
ALBUM
10_
ALBUM
: Folder
: MP3 file
001TRACK.MP3
002TRACK.MP3
...
010TRACK.MP3
...
...
FAQ- about MP3 Audio File


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CDX-757MX
TABLE OF CONTENTS
SERVICING NOTES .......................................................... 2
1.
GENERAL
Installation .......................................................................
6
Connections .....................................................................
7
2.
DISASSEMBLY
2-1. Disassembly Flow ...........................................................
8
2-2. Case (Upper. T), Front Panel Assy .................................
9
2-3. Mechanism Deck (MG-251B-137) .................................
9
2-4. JACK Board .................................................................... 10
2-5. MAIN Board, Slide Variable Resistor
(Elevator Height Sensor) (RV202) ................................. 10
2-6. ELJ Motor Assy (Elevator) (M104) ................................ 11
2-7. Escutcheon (T) ................................................................ 11
2-8. Chassis (U.S) Sub Assy .................................................. 12
2-9. Chassis Assy .................................................................... 12
2-10. RF Board ......................................................................... 13
2-11. Sled Motor Assy (251) (M101),
Optical Pick-up (KSS-720A) .......................................... 13
2-12. LSW Board, Spindle Motor (S) Sub Assy (M102) ........ 14
2-13. ELJ Motor Assy (Chucking) (M103) ............................. 14
3.
ASSEMBLY
3-1. Assembly Flow ................................................................ 15
3-2. Optical Pick-up Complete Assy ...................................... 15
3-3. Gear (Lomini)/(Load 1) Assy ......................................... 16
3-4. Operation Check ............................................................. 16
4.
MECHANICAL ADJUSTMENT .......................... 17
5.
ELECTRICAL CHECK .......................................... 18
6.
DIAGRAMS
6-1. Block Diagram ­ SERVO Section ­ .............................. 20
6-2. Block Diagram ­ MAIN Section (1/2) ­ ....................... 21
6-3. Block Diagram ­ MAIN Section (2/2) ­ ....................... 22
6-4. Note for Printed Wiring Boards and
Schematic Diagrams ....................................................... 23
6-5. Printed Wiring Boards ­ RF/LSW Boards ­ ................. 24
6-6. Schematic Diagram ­ RF/LSW Boards ­ ...................... 25
6-7. Printed Wiring Boards
­ MAIN Board (Component Side) ­ .............................. 26
6-8. Printed Wiring Boards
­ MAIN (Conductor Side)/SWITCH Boards ­ .............. 27
6-9. Schematic Diagram ­ MAIN Board (1/3) ­ .................. 28
6-10. Schematic Diagram
­ MAIN (2/3)/SWITCH Boards ­ .................................. 29
6-11. Schematic Diagram ­ MAIN Board (3/3) ­ .................. 30
6-12. Printed Wiring Boards ­ JACK Board ­ ........................ 32
6-13. Schematic Diagram ­ JACK Board ­ ............................. 33
6-14. IC Pin Function Description ........................................... 39
7.
EXPLODED VIEWS
7-1. Case Section .................................................................... 41
7-2. Mechanism Deck Section-1 (MG-251B-137) ................ 42
7-3. Mechanism Deck Section-2 (MG-251B-137) ................ 43
7-4. Mechanism Deck Section-3 (MG-251B-137) ................ 44
7-5. Mechanism Deck Section-4 (MG-251B-137) ................ 45
8.
ELECTRICAL PARTS LIST ............................... 46