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SERVICE MANUAL Model Series:
L20V26
Product Type: LCD TV
Chassis: MF-002A
Manual Series: CM154
Manual Part #: 923-03488
Model Line: E
Product Year: 2002
CONTENTS
Safety .......................................................... 2
Overview ...................................................... 5
Servicing ................................................... 12
Parts ......................................................... 13
Diagrams .................................................... 19
Schematic .................................................. 25
Published June 2002
by Technical Publications
Zenith Electronics Corporation
201 James Record Road
Huntsville, Alabama 35824-1513
Printed in U.S.A.
Copyright 2002 by Zenith Electronics Corporation
PRODUCT SAFETY
PRODUCT SAFETY 1. Immediately before handling any semiconductor component or
semiconductor-equipped assembly, drain off any electrostatic charge
IMPORTANT SAFETY NOTICE on the body by touching a known earth ground. Alternatively, ob-
This manual was prepared for use only by properly trained audio- tain and wear a commercially available discharging wrist strap de-
visual service technicians. When servicing this product, under no vice, which should be removed for potential shock reasons prior to
circumstances should the original design be modified or altered applying power to the unit under test.
without permission from Zenith Electronics Corporation. All 2. After removing an electrical assembly equipped with ES devices,
components should be replaced only with types identical to those place the assembly on a conductive surface such as an ESD mat, to
in the original circuit and their physical location, wiring, and lead prevent electrostatic charge buildup or exposure of the assembly.
dress must conform to original layout upon completion of repairs. If
any fuse (or Fusible Resistor) in this TV receiver is blown, replace it 3. Use only a grounded-tip soldering iron to solder or unsolder ES
only with the factory specified fuse type and rating. When replacing devices.
a high wattage resistor (Oxide Metal Film Resistor, over 1W), keep the 4. Use only an anti-static solder removal device. Some solder re-
resistor 10mm away from PCB. Always keep wires away from high moval devices not classified as "anti-static" can generate electrical
voltage or high temperature parts. charges sufficient to damage ES devices.
Special components are also used to prevent shock and fire hazard. 5. Do not use freon-propelled chemicals. These can generate electri-
These components are indicated by the letter "x" included in their cal charge sufficient to damage ES devices.
component designators and are required to maintain safe
6. Do not remove a replacement ES device from its protective pack-
performance. No deviations are allowed without prior approval by
age until immediately before you are ready to install it. (Most re-
Zenith Electronics Corporation. Service work should be performed
placement ES devices are packaged with leads electrically shorted
only after you are thoroughly familiar with these safety checks and
together by conductive foam, aluminum foil, or comparable con-
servicing guidelines.
ductive material.)
Circuit diagrams may occasionally differ from the actual circuit used.
7. Immediately before removing the protective material from the
This way, implementation of the latest safety and performance
leads of a replacement ES device, touch the protective material to
improvement changes into the set is not delayed until the new
service literature is printed. the chassis or circuit assembly into which the device will be in-
stalled.
CAUTION: Do not attempt to modify this product in any way. Never
perform customized installations without manufacturer's approval. Caution: Be sure no power is applied to the chassis or circuit, and
Unauthorized modifications will not only void the warranty, but observe all other safety precautions.
may lead to property damage or user injury. 8. Minimize bodily motions when handling unpackaged replace-
ment ES devices. (Otherwise, seemingly harmless motion, such as the
GENERAL GUIDANCE
brushing together of your clothing or the lifting of your foot from a
An lsolation Transformer should always be used during the servicing carpeted floor, can generate static electricity sufficient to damage
of a receiver whose chassis is not isolated from the AC power line. Use an ES device.)
a transformer of adequate power rating to protect against personal
injury from electrical shocks. It will also protect the receiver and its REGULATORY INFORMATION
components from being damaged by accidental shorts of the circuitry This equipment has been tested and found to comply with the limits
that may be inadvertently introduced during the service operation. for a Class B digital device, pursuant to Part 15 of the FCC Rules.
Before returning the receiver to the customer, always perform an AC These limits are designed to provide reasonable protection against
leakage current check on the exposed metallic parts of the cabinet, harmful interference when the equipment is operated in a residential
such as antennas, terminals, etc., to be sure the set is safe to operate installation. This equipment generates, uses and can radiate radio
without damage of electrical shock. frequency energy and, if not installed and used in accordance with
the instruction manual, may cause harmful interference to radio
LEAKAGE CURRENT COLD CHECK (ANTENNA COLD CHECK) communications. However, there is no guarantee that interference
With the instrument AC plug removed from AC source, connect an will not occur in a particular installation. If this equipment does
electrical jumper across the two AC plug prongs. Place the AC switch cause harmful interference to radio or television reception, which
in the on position, connect one lead of ohm-meter to the AC plug can be determined by turning the equipment off and on, the user is
prongs tied together and touch other ohm-meter lead in turn to encouraged to try to correct the interference by one or more of the
each exposed metallic parts such as antenna terminals, phone jacks, following measures: Reorient or relocate the receiving antenna; In-
etc. If the exposed metallic part has a return path to the chassis, the crease the separation between the equipment and receiver; Connect
measured resistance should be between 1M and 5.2M. When the the equipment into an outlet on a circuit different from that to
exposed metal has no return path to the chassis the reading must be which the receiver is connected; Consult the dealer or an experi-
infinite. Any other abnormality that exists must be corrected before enced radio/TV technician for help.
the receiver is returned to the customer. The responsible party for this device's compliance is:
ELECTROSTATICALLY SENSITIVE DEVICES Zenith Electronics Corporation
Some semiconductor (solid-state) devices can be damaged easily by 201 James Record Road
static electricity. Such components commonly are called Electro- Huntsville, AL 35824, USA
statically Sensitive (ES) Devices. Examples of typical ES devices are Digital TV Hotline: 1-800-243-0000
integrated circuits and some field-effect transistors and semicon-
ductor "chip" components. The following techniques should be
used to help reduce the incidence of component damage caused by
static electricity.
CM154 - 923-03488 2 L20V26 - SAFETY
TABLE OF CONTENTS
PRODUCT SAFETY ................................................ 2
TABLE OF CONTENTS ............................................ 3
OVERVIEW ........................................................ 5
WARRANTY/SERVICE ........................................ 5
FEATURES ..................................................... 5
SPECIFICATIONS ............................................. 5
REMOTE CONTROL ........................................... 6
FRONT .......................................................... 7
BACK ........................................................... 7
USER MENUS ..................................................... 8
MENU LANGUAGE ............................................ 8
CLOSED CAPTIONING ....................................... 8
PARENTAL CONTROL ........................................ 9
CHANNEL SEARCH ........................................... 9
SLEEP TIMER ............................................... 10
AUDIO SETUP .............................................. 10
VIDEO ........................................................ 11
SERVICING ...................................................... 12
ADJUSTMENTS .............................................. 12
PARTS ............................................................ 13
MODEL PARTS .............................................. 13
COMPONENT PARTS ....................................... 13
DIAGRAMS ...................................................... 19
EXPLODED VIEW ........................................... 19
BLOCK DIAGRAM .......................................... 20
MAIN PCB LAYOUT ........................................ 21
MX PCB LAYOUT ........................................... 22
TUNER PCB LAYOUT ....................................... 23
CONTROL PANEL PCB LAYOUT .......................... 23
MAIN L20V26 CIRCUIT ...................................... 25
CM154 - 923-03488 3 L20V26 - TOC
-4-
OVERVIEW
GENERAL INFO NTSC TUNER
Accepts standard United States broadcast video
WARRANTY/SERVICE signals as designated by the National Television
This model is a Factory Service Repair model (in and out Standards Committee.
of warranty) and is covered by a one year limited
HI-RES COMPONENT VIDEO
warranty. For service, the end user should call 1-800-
Delivers the highest quality picture by breaking down
984-9349 for complete shipping and handling
video data into three separate signals--red, blue and
instructions (or call 1-877-9ZENITH). Refer to the last
luminance--before the data is sent to the television.
page of the opguide for more information.
SPECIFICATIONS
FEATURES
VIDEO ENHANCEMENTS
20.1" EDTV MONITOR Screen Size ............................................... 20.1"
Truly Flat LCD screen delivers razor sharp images.
Flat ............................................................. Yes
BUILT IN NTSC TUNER
Resolution Display ...................... 640 x 480 (VGA)
Accepts cable/antenna, HDTV, satellite dish,
Color Depth ..................................... 16M (8-Bit)
and NTSC video sources
Aspect Ratio ................................................ 4:3
640 X 480 RESOLUTION
High resolution format produces extremely Contrast Ratio ........................................... 400:1
detailed imagery Brightness ........................................ 450 cd/m2
400:1 HIGH CONTRAST RATIO High Drive Video Watts ................................ 70W
LCD technology emits sharp contrast Viewing Angle .................................. 140