Toshiba WL56 Series User manual

SERVICE MANUAL
LCD Color Television
37WL58P
FILE NO. 030-200505
Published in Japan Sep. 2005 (YC)TOSHIBA CORPORATION 2005

– 2 –
TABLE OF CONTENTS
SERVICE SAFETY PRECAUTIONS .................................................................................................................................... 3
HANDLING THE LCD MODULE .......................................................................................................................................... 5
SERVICE MODE .................................................................................................................................................................. 7
LOCATION OF CONTROLS ...............................................................................................................................................12
LAYOUT OF MAJOR BOARDS .......................................................................................................................................... 14
MECHANICAL DISASSEMBLY .......................................................................................................................................... 15
EXPLODED VIEWS............................................................................................................................................................ 17
PACKING DISASSEMBLY ................................................................................................................................................. 19
CHASSIS AND CABINET REPLACEMENT PARTS LIST ................................................................................................. 20
PC BOARDS TOP & BOTTOM VIEW ................................................................................................................................ 29
CIRCUIT BLOCK DIAGRAM .............................................................................................................................................. 45
SPECIFICATIONS ............................................................................................................................................................. 49
APPENDIX:
SCHEMATIC DIAGRAM

–3 –
GENERAL ADJUSTMENTS
SPECIFIC INFORMATIONS
SERVICE SAFETY PRECAUTIONS
•The caution items shown here describe major safety issues and should always be observed.
•The meanings of the various indications are as follows.
WARNING
CAUTION
Indicates a hypothetical situation in which service personnel and nearby third parties, or even
end users due to a product defect after the service operation is completed, could possibly be in
danger of injury or even death in the event of operational error.
Indicates a hypothetical situation in which service personnel and nearby third parties, or even
end users after the service operation is completed, could possibly be in danger of injury, or
where there could be physical damage in the event of operational error.
* Physical damage means major damage to a home, furnishings and other possessions.
Examples of marks
SHOCK HAZARD
PROHIBIT DISASSEM-
BLING
UNPULUG
The " indicates caution (including danger and warning).
The actual meaning of this caution is indicated inside the
" or nearby illustrations or text.
The example shown to the left indicates the danger of "electrical shock".
The indicates a forbidden action.
The actual meaning of this caution is indicated inside the or nearby illustrations or text.
The example shown to the left indicates that disassembly is forbidden.
The
- indicates a forced action (an action that must be performed).
The actual meaning of this forced action is indicated by
- or nearby illustrations or text.
The example shown to the left indicates that the power plug must be disconnected.

–4 –
WARNING
KEEP CHILDREN
AWAY
UNPULUG
SHOCK HAZARD
USE SPECIFIED
PARTS
CAUTION FOR
WIRING
CAUTION FOR
ASSEMBLING /
WIRING
CHECK INSULATION
RESISTANCE
PROHIBIT
REMODELING
•Always advise users to keep children away.
There is danger of injury to children from tools, disassembled products, etc.
•Always disconnect the power plug before starting work whenever power is not required.
Failure to disconnect the power plug before starting work can result in electrical shock.
•Depending on the model, use an insulation transformer or wear gloves when servicing with the
power on, and disconnect the power plug to avoid electrical shock when replacing parts.
In some cases, alternating current is also impressed in the chassis, so electrical shock is pos-
sible if the chassis is contacted with the power on.
•Always use the replacement parts specified for the particular model when making repairs.
The parts used in products have the necessary safety characteristics such as inflammability,
voltage resistance, etc.; therefore, use only replacement parts that have these same character-
istics.
Use only the specified parts when the mark is included in a circuit diagram or parts list.
•Parts mounting and routing of the wiring should be the same as that used originally.
For safety purposes, insulating materials such as tubing or tape is sometimes used and printed
circuit boards are sometimes mounted floating.
Also make sure that wiring is routed and clamped to avoid parts that generate heat and which
use high voltage. Always follow the original scheme.
•After a repair has been completed, reassemble all disassembled parts, and route and recon-
nect the wiring, in accordance with the original scheme.
Do not allow internal wiring to be pinched by cabinets, panels, etc.
Any error in reassembly or wiring can result in electrical leakage, flame, etc., and may be
hazardous.
•After completing the work, disconnect the power plug from the outlet, remove the antenna, turn
on the power switch. Then, use a 500V insulation resistance meter to check the insulation
resistance of the antenna terminal, other metallic parts and between the prongs of the power
plug to make sure that the insulation resistance is 1M 1or more.
The set will require inspection and repair if the insulation resistance is below this value.
•Never remodel the product in any way.
Remodeling can result in improper operation, malfunction, or electrical leakage and flame,
which may be hazardous

–5 –
GENERAL ADJUSTMENTSSPECIFIC INFORMATIONS
HANDLING THE LCD MODULE
Safety Pre autions
In the event that the screen is damaged or the liquid crystal
(fluid) leaks, do not breathe in or drink this fluid. Also, never
touch this fluid.
Such actions could cause toxicity or skin irritation. If this fluid
should enter the mouth, rinse the mouth thoroughly with wa-
ter. If the fluid should contact the skin or clothing, wipe off
with alcohol, etc., and rinse thoroughly with water. If the fluid
should enter the eyes, immediately rinse the eyes thoroughly
with running water.
Pre autions for Handling the LCD Module
The LCD module can easily be damaged during disassembly
or reassembly; therefore, always observe the following pre-
cautions when handling the module.
1. When attaching the LCD module to the LCD cover, posi-
tion it appropriately and fasten at the position where the
display can be viewed most conveniently.
2. Carefully align the holes at all four corners of the LCD
module with the corresponding holes in the LCD cover
and fasten with screws. Do not strongly push on the mod-
ule because any impact can adversely affect the perform-
ance. Also use caution when handling the polarized screen
because it can easily be damaged.
CAUTION The metal edges of the LCD module
are sharp, so use caution to avoid in-
jury.
3. If the panel surface becomes soiled, wipe with cotton or a
soft cloth. If this does not remove the soiling, breathe on
the surface and then wipe again.
If the panel surface is extremely solied, use a CRT cleaner
as a cleaner.Wipe off the panel surface by drop the cleaner
on the cloth. Do not drop the cleaner on the panel. Pay
attention not to scratch the panel surface.
4. Leaving water or other fluids on the panel screen for an
extended period of time can result in discoloration or
stripes. Immediately remove any type of fluid from the
screen.
5. Glass is used in the panel, so do not drop or strike with
hard objects. Such actions can damage the panel.
6. CMOS-LSI circuitry is used in the LCD module, so avoid
damage due to static electricity. When handling the mod-
ule, use a wrist ground or anchor ground.

–6 –
7. Do not expose the LCD module to direct sunlight or strong
ultraviolet rays for an extended period of time.
8. Do not store the LCD module below the temperature con-
ditions described in the specifications. Failure to do so
could result in freezing of the liquid crystal due to cold air
or loss of resilience or other damage.
9. Do not disassemble the LCD module. Such actions could
result in improper operation.
10. When transporting the LCD module, do not use packing
containing epoxy resin (amine) or silicon resin (alcohol or
oxim). The gas generated by these materials can cause
loss of polarity.

–7 –
Test signal selection : abutton (on Remote)
Selection of the adjustment items : Channel s/t(on TV or Remote)
Change of the data value : Volume ;+/–(on TV or Remote)
Adjustment menu mode ON/OFF : MENU button (on TV)
Initialization of the memory : CALL + Channel button on TV (s)
Reset the count of operating protect
circuit to “00”: CALL + Channel button on TV (t)
“RCUT”selection : 1 button
“GCUT”selection : 2 button
“BCUT”selection : 3 button
“SCNT”selection : 4 button
“COLP”selection : 5 button
“TNTC”selection : 6 button
Color thickness correction
note: Displayed differently as shown below, de-
pending on the setting of the receiving color
system.
COLP (PAL)
COLC (NTSC)
COLS (SECAM)
Automatic A/D Adjustment(PC, Component) : 7 button
Self diagnostic display ON/OFF : 9 button
CAUTION : Never try to perform initialization unless you have changed the memory IC.
SERVICE MODE
1. ENTERING SERVICE MODE
1) Press button once on 2) Press button again and 3) While pressing the button,
Remote Control. keep pressing. press MENU button on TV set.
(Service mode display)
2. DISPLAYING THE ADJUSTMENT MENU
1) Press MENU button on TV.
Service mode Adjustment mode
3. KEY FUNCTION IN THE SERVICE MODE
The following key entry during display of adjustment menu provides special functions.
Press
Press
or Sound Mute

–8 –
4. SELECTING THE ADJUSTING ITEMS
1) Every pressing of CHANNEL sbutton in the service mode changes the adjustment items in the order of table-2.
(tbutton for reverse order)
5. ADJUSTING THE DATA
1) Pressing of VOLUME ;+/–button will change the value of data in the range from 00H to FFH. The variable range
depends on the adjusting item.
6. EXIT FROM SERVICE MODE
1) Pressing POWER button to turn off the TV once.
■INITIALIZATION OF MEMORY DATA
After replacing EEPROM IC, the following initialization is required.
1. Enter the service mode, then select any register item.
2. Press and hold the CALL button on the Remote, then press the CHANNEL sbutton on the TV.The initialization of EEPROM IC
has been complated.
3. Check the picture carefully. If necessary, adjust any adjustment item above.
Perform “Auto tune”on the owner’s manual.
CAUTION: Never attempt to initialize the data unless EEPROM IC has been replaced.
7. TEST SIGNAL SELECTION
1) Every pressing of abutton on the Remote Control changes the built-in test patterns on screen as described below
in SERVICE MODE.
Signals Picture
•Red raster
•Green raster
•Blue raster
•All Black
•All White
R
All BlackAll White
BSignal off G

–9 –
8. SELF DIAGNOSTIC FUNCTION
1) Press “9”button on Remote Control during display of adjustment menu in the service mode.
The diagnosis will begin to check if interface among IC’s is executed properly.
2) During diagnosis, the following displays are shown.
Firmware :
Version information of microprocessor
In case of file name : WL58_EU and Version : 0100 indicates[WL58_EU_0100].
Time : Total hour of turn the TV on. (Unit : H)
Power :Operation number of protecting circuit ----"000" is normal.
When indication is other than "000", overcurrent apt to flow, and circuit parts may possibly be damaged.
Bus line : --"OK" is normal
"SCL-GND"(Red indication) : SCL-GND short circuit
"SDA-GND"(Red indication) : SDA-GND short circuit
"SCL-SDA"(Red indication) : SCL-SDA short circuit
Bus cont : --- "OK" is normal.
NG is abnormal(Red indication), when
type name of semiconductor indicates.
Block
UV : TV reception mode
V1 : VIDEO 1 input mode ( 1)
V2 : VIDEO 2 input mode ( 2)
V3 : VIDEO 3 input mode ( 3)
V4 :COMPONENT VIDEO input mode ( 4)
8 digit : CD number
Model name (7 digit)
V5: VIDEO 5input mode ( 5)
1
2
3
4
5
6
1
2
3
4
5
6
78
7
8

–10 –
9. VERSION CHECK MODE
1) Press “9”button twice on Remote Control during display of adjustment menu in the service mode. The version of main
MPU will begin to check.
2) During Version Check, the following displays are shown.
MMAIN MPU :
Version information of microprocessor
In case of file name : WL58_EU, Version 0100 for Code Program Version
and (E16) for OSD Version indicates [WL58_EU_0100(E16)]
NEEPROM :
Version information of EEPROM : Display 1 byte data.
OSUB MPU :
Version information of SUB MPU : Display 1 byte data.
POPTION :
Option information : Display six numbers of 1 byte data.
QHDMI ID :
HDMI ID information : Display 4 byte data.
RCD number : Display 8 digit number
SModel name : Display 7 digit number
TPanel Vender information display
The following Panel Vender and screen size are displayed.
M
N
O
P
Q
R
ST
Example : SHP-37indicates that Vender is SHP and Screen Size is 37inch.
Panel Vender Screen Size(Inch)
LPLLCD
PDP
-23
SHP -26
CMO
LG
-32
-37
-42
-42
Panel

–11 –
10. STATUS CHECK MODE
1) Press “9”button thrice on Remote Control during display of adjustment menu in the service mode. The status of this model
will begin to check.
2) During Status Check, the following displays are shown.
MMAIN :
Main source information :
Display RF position number (0 - 99) on the main screen, or Input Source (EXT1/2/3/HDMI etc.)
NMAIN FORMAT :
Display Video and PC format information
OMAIN PLL :
Main PLL information : Display five numbers of 1 byte data.
PSCREEN SIZE :
Display the screen size as follows.
QOTHER STATUS :
Other status information : Display three numbers of 2 byte data.
Super live
Cinema
Subtitle
14:9
Wide
4:3
EXT1
1080i-50
C6 38 54 CE 08
0000 0000 0000
1
2
4
5
3

–12 –
Standby
GREEN – On-timer set
RED – Power On
INPUT 5
(EXT5)
media recorder
decoder*
CABLE HOLDER
FIXING STRAP
HDMITM INPUT SOCKETS
SCART 2 (EXT2)
SCART 3 (EXT3)
SCART 1 (EXT1)
I N/ O U T
M E DIA R E C .
T V
S AT
LOCATION OF CONTROLS
Front
Back

–13 –
Remote ontrol
To mute the sound
Text control buttons
To exit Menus
Bass Boost/Super Woofer
Stereo/Bilingual reception
To bring up on-screen information and
for the text initial/index function
To select input from external sources
To access sub-pages when in text mode
To select mode
On-screen Menus
Selectable picture preferences Widescreen viewing
Number buttons
To return to the previous programme
For On/Standby mode
To display text services
When using a TOSHIBA VCR or DVD:
press
mto PAUSE
presswto EJECT
press
l
qto SKIP-REWIND
presss
l
to SKIP-FORWARD
press rto PLAY
presspto STOP
press qto REWIND
presssto FAST FORWARD
To change programme positions and
text pages
To alter the volume
When using menus the arrows move the
cursor on the screen up, down, left or
right. OK to confirm your selection
When in TV mode:
8/9
Time display
When in Text mode:
rTo reveal concealed text
qTo hold a wanted page
sTo enlarge text display size
8/9
To select a page whilst viewing a
normal picture

– 14 –
LAYOUT OF MAJOR BOARDS
U003E
PC HDMI BOARD
U003B
FRONT AV BOARD
U001
SIGNAL BOARD U002A
POWER BOARD
U002B
AC IN BOARD
U003C
RMT LED BOARD
U003A
TN AV BOARD
U004
LOW B BOARD
U003D
KEY BOARD

–15 –
MECHANICAL DISASSEMBLY
1. Remove the stand (foot) and back cover.
PP 5×16 SW+W SBN
×5
PP3×8
+SW+W SBN
×5
BITTB4×16 SBN
×10
A401
A450
A445
A420
2. Remove the boards (FRONT AV,PC HDMI, KEY) and back center cover.
U003E
U003D
A340
A320
A315
U003B
P809B
PP3×8+SW+W SBN
×2
PP3×8+SW+W SBN
×2
PP3×8+SW+W SBN
×2PP3×8
+SW+W SBN
×2
PP3×8+SW+W SBN
×2
PP3×8
+SW+W SBN
×2
BITTB
3×12SBN
×2
BITTB3×12SBN
×2BITTB4×16 SBN
×2
BITTB4×16 SBN
×2

–16 –
3. Remove the boards (POWER, AC-IN, SIGNAL, LOW B,TN AV, RMT LED) and speaker.
4. Remove the display.
U002B
U003C
W661
W661
U003A
U004
U002A
U001
PP3×8+SW+W SBN
×6
PP3×8+SW+W SBN
×4
PP3×8+SW+W SBN
×8
PP3×8
+SW+W SBN
×4
PP3×8
+SW+W SBN
×2
BITTB3×12SBN
×3
BITTB4×16 SBN
×2
BITTB4×16 SBN
×2
A201
B001
BITTB4×16 SBN
×12
BITTB4×16
SBN×4

– 17 –
EXPLODED VIEWS
1. Chassis Block
U003D
A340
A401
BITTB3×12SBN
×2
BITTB4×16 SBN
×2
U003E
PP3×8+SW+W SBN
×2
BITTB3×12SBN
×2
PP3×8+SW+W SBN
×2
PP3×8+SW+W SBN
×5
PP 5×16 SW+W SBN
×5
A320
A420
U003B
PP3×8+SW+W SBN
×2PP3×8
+SW+W SBN
×2
PP3×8+SW+W SBN
×2
PP3×8+SW+W SBN
×2
BITTB4×16 SBN
×10
A450
A445

–18 –
2. Main Block
BITTB4×16 SBN
×2
U002A
PP3×8+SW+W SBN
×8
U004
PP3×8+SW+W SBN
×4
U002B
PP3×8+SW+W
SBN×2
U001
PP3×8+SW+W SBN
×4
BITTB4×16 SBN
×12
U003A
PP3×8+SW+W SBN
×6
W661
BITTB4×16 SBN
×2
W661
BITTB4×16 SBN
×2
U003C
BITTB3×12SBN
×3
P809B
A315
B001
A201
BITTB4×16
SBN×4

- 19 -
PACKING DISASSEMBLY
Y130Y170 Y101E
Y101
A701A
A705
A705
A701B
A702B
A702B
A702A
A702A

WARNING: BEFORE SERVICING THIS CHASSIS, READ THE "SERVICE SAFETY PRECAUTIONS" ON PAGE 3 OF
THIS MANUAL.
CAUTION: The international hazard symbols " " in the schematic diagram and the parts list designate components
which have special characteristics important for safety and should be replaced only with types identical to those in the
original circuit or specified in the parts list. The mounting position of replacements is to be identical with originals.
Before replacing any of these components, read carefully the PRODUCT SAFETY NOTICE. Do not degrade the safety
of the receiver through improper servicing.
NOTICE:
••
••
• The part number must be used when ordering parts, in order to assist in processing, be sure to include the
Model number and Description.
••
••
• The PC board assembly with *mark is no longer available after the end of the production.
Capacitors ............. CD : Ceramic Disk PF : Plastic Film EL : Electrolytic
Resistors ............... CF : Carbon Film CC : Carbon Composition MF : Metal Film
OMF : Oxide Metal Film VR : Variable Resistor FR : Fusible Resistor
(All CD and PF capacitors are ±5%, 50V and all resistors, ±5%, 1/6W unless otherwise noted.)
– 20 –
Location Parts No. Description
No.
Location Parts No. Description
No.
Model : 37WL58P
CHASSIS AND CABINET REPLACEMENT PARTS LIST
CAPACITORS
C101 76109103 CERAMIC CHIP, 50V B 0.01UF K
C102 76073019 ELECTROLYTIC, 10V 470UF M 3A
C103 76109102 CERAMIC CHIP, 50V B 1000PF K
C104 76619143 ELECTROLYTIC CHIP, 50V 4.7UF M
C105 76073019 ELECTROLYTIC, 10V 470UF M 3A
C113 76109102 CERAMIC CHIP, 50V B 1000PF K
C117 76109103 CERAMIC CHIP, 50V B 0.01UF K
C118 76109103 CERAMIC CHIP, 50V B 0.01UF K
C162 76105101 CERAMIC CHIP, 50V CH 100PF J
C164 76100103 CERAMIC CHIP, 50V F 0.01UF Z
C190 76092730 CERAMIC CHIP, 16V B 0.1UF K
C501 76100104 CERAMIC CHIP, 25V F 0.1UF Z
C502 76100104 CERAMIC CHIP, 25V F 0.1UF Z
C503 76619046 ELECTROLYTIC CHIP, 16V 470UF
C504 76109103 CERAMIC CHIP, 50V B 0.01UF K
C505 76619046 ELECTROLYTIC CHIP, 16V 470UF
C506 76109103 CERAMIC CHIP, 50V B 0.01UF K
C514 76665221 ELECTROLYTIC, 10V 220UF M 3A
C516 76105110 CERAMIC CHIP, 50V CH 11PF J
C517 76092785 CERAMIC CHIP, 10V B 0.47UF K
C519 76619048 ELECTROLYTIC CHIP, 25V 4.7UF M
C521 76092733 CERAMIC CHIP, 50V B 0.022UF K
C524 76109103 CERAMIC CHIP, 50V B 0.01UF K
C526 76109103 CERAMIC CHIP, 50V B 0.01UF K
C527 76619071 ELECTROLYTIC CHIP, 50V 2.2UF
C529 76100104 CERAMIC CHIP, 25V F 0.1UF Z
C530 76619157 ELECTROLYTIC CHIP, 16V 100UF
C605 76109102 CERAMIC CHIP, 50V B 1000PF K
C606 76109102 CERAMIC CHIP, 50V B 1000PF K
C612 76664102 ELECTROLYTIC, 6.3V 1000UF M 3A
C631 76619102 ELECTROLYTIC CHIP, 16V 47UF M
C632 76092731 CERAMIC CHIP, 16V B 1UF K
C651 76092463 CERAMIC CHIP, 16V B 0.22UF K
C652 76092463 CERAMIC CHIP, 16V B 0.22UF K
C653 76092538 CERAMIC CHIP, 10V F 1UF Z
C655 76109103 CERAMIC CHIP, 50V B 0.01UF K
C661 76109102 CERAMIC CHIP, 50V B 1000PF K
C662 76109102 CERAMIC CHIP, 50V B 1000PF K
C663 76619100 ELECTROLYTIC CHIP, 16V 10UF M
C665 76669479 ELECTROLYTIC, 50V 4.7UF M
C666 76669479 ELECTROLYTIC, 50V 4.7UF M
C671 76669100 ELECTROLYTIC, 50V 10UF M
C674 76669100 ELECTROLYTIC, 50V 10UF M
C677 76109681 CERAMIC CHIP, 50V B 680PF K
C678 76109681 CERAMIC CHIP, 50V B 680PF K
C680 76668102 ELECTROLYTIC, 35V 1000UF M 3A
C681 76668102 ELECTROLYTIC, 35V 1000UF M 3A
C682 76668102 ELECTROLYTIC, 35V 1000UF M 3A
C690 76815103 CERAMIC CHIP, 50V B 0.01UF K
C694 76285104 CERAMIC CHIP, 50V B 0.1UF K
C696 76285104 CERAMIC CHIP, 50V B 0.1UF K
C801 76168007 MT PLA AC275V 1UF M
C802 76503508 MT PLA PCX2 337 11474
C806 76092555 CERAMIC DISC, AC250V E 1000PF M
C807 76092555 CERAMIC DISC, AC250V E 1000PF M
C808 76092553 CERAMIC DISC, AC250V B 470PF K
C809 76092553 CERAMIC DISC, AC250V B 470PF K
C812 76109102 CERAMIC CHIP, 50V B 1000PF K
C814 76109102 CERAMIC CHIP, 50V B 1000PF K
C815 76073037 ELECTROLYTIC, 16V 47UF M 3A
C815A 23960136 ADHESIVE, SILICONE, TSE3843-W
C816 76109102 CERAMIC CHIP, 50V B 1000PF K
C817 76109102 CERAMIC CHIP, 50V B 1000PF K
C818 76669010 ELECTROLYTIC, 50V 1UF M
C819 76539684 PLASTIC FILM, 50V 0.68UF J
C820 76125010 CHEMICON CE69R 450V 270UF M 3H
C821 76125011 CHEMICON CE04R 450V 82UF M 4A
C822 76214103 CERAMIC DISC, 500V B 0.01UF K
C824 76168008 MT PLA 450V 1UF K
C825 76168008 MT PLA 450V 1UF K
C826 76092339 CERAMIC DISC, 2KV 330PF K
C827 76092339 CERAMIC DISC, 2KV 330PF K
C840 76125009 CHEMICON 450V 47UF M
C843 76166001 CERAMIC DISK CC45 SL 3.15KV 47PF J
C844 76669479 ELECTROLYTIC, 50V 4.7UF M
C845 76073196 ELECTROLYTIC, 50V 22UF M 3A
C846 76073140 ELECTROLYTIC CE04P 10V 680UF M 3A
C847 76665471 ELECTROLYTIC, 10V 470UF M
C848 76214471 CERAMIC DISC, 500V B 470PF K
C849A 23960136 ADHESIVE, SILICONE, TSE3843-W
C860 76214103 CERAMIC DISC, 500V B 0.01UF K
C861 76503053 PLASTIC FILM, 63V 1UF J
C862 76669229 ELECTROLYTIC, 50V 2.2UF M
C863 76503049 PLASTIC FILM, 63V 0.47UF J
C864 76567224 PLASTIC FILM, 50V 0.22UF J
C865 76567224 PLASTIC FILM, 50V 0.22UF J
C866 76092341 CERAMIC DISC, 2KV R 470PF K
C868 76435221 CERAMIC DISC, 500V SL 220PF J
C869 76435221 CERAMIC DISC, 500V SL 220PF J
C870 76503425 PLASTIC FILM CQ92 3D2J473J-K5
C872 76073189 ELECTROLYTIC, 35V 1000UF M