LG LHT754 Service Manual

LHT754

Home Theater

In A Box

Troubleshooting

Home Theatre Troubleshooting - 2007

Overview of Topics to be

Discussed

•Features

•Power Supply

Home Theatre Troubleshooting - 2007

•Front Display

•Loader

•Amplifier Section

•Main Control

Safety Rules

Home Theatre Overview

Safety & Handling Regulations

1. Approximately 10 minute pre-run time is required before any adjustments are performed.

2. Do not exceed Higher voltage than is required for the product.

3. Be cautious of electric shock from the PBC modules since the modules use high voltage, and it is
recommended that you should not touch the drive circuits for at least one minute because of residual
current stored.

4. Circuit drive has c-mos circuits which should be protected from static electricity.

5. Be careful of short circuits when measuring voltages.

6. Be cautious of screws and other metal objects to prevent a short in the circuitry.

Troubleshooting

Checking Point before Replacing PCB Modules

1. Check the appearance of Power Supply and PCB's

2. Check the model label. Verify model names and board model matches.

3. Check details of defective condition and history.
IE: Software Updates, Service Bulletins

Home Theatre Troubleshooting - 2007

Model : LHT754

1000 WATT HOME THEATER SYSTEM

1000W TOTAL POWER

Powerful sound with 1000 watts of total output power.

MADE FOR iPOD

Connect, control and play directly from your iPod.

1080i UP-CONVERSION

Superior image quality and convenience with 1080i up conversion via
HDMI™ output.

USB MEDIA PLUS

Experience your digital music, photo and video library with USB Media Plus.

XM READY*

Enjoy hundreds of channels of XM Satellite Radio (subscription required)
with an optional XM Mini-Tuner Antenna.

Home Theatre Troubleshooting - 2007

LG SIMPLELINK

Allows for convenient control of other LG SimpLink products using the
existing HDMI™ connection.

MSRP : $329.95

FEATURES

Home Theatre Troubleshooting - 2007

DVD Specifications

The DVD specification supports the MPEG video information on a DVD disc in one of the two formats
required for incompatible television systems: the 525/60 NTSC or 6 25/50 PAL/SECAM video standard.
The program material recorded on a DVD disc can belong to only one of the two video standard s ,
not both. This restriction applies to only one side of the DVD. If a DVD disc is double-sided, the video
on one side can be recorded in 525/60 NTSC format, and the video on the other side can be 625/50 PAL.
This is because the contents on one side are unrelated to the contents on the opposite side. However,
such a disc is rare in production. In general, there are two types of DVD-Video discs commonly known
as NTSC DVDs and PAL DVDs.

There are three major differences between DVD discs designed for playback on different television
systems:

1: Picture Dimensions and pixel aspect ratio

(720x480 NTSC, 720x576 PAL),

2: Display frame rate (29.97 frames/sec NTSC, 25 frames/sec PAL),

3: The default audio options (Dolby Digital with NTSC video, MPEG audio with PAL video).
All PAL DVD players can play Dolby Digital audio tracks, but not all NTSC players can
play MPEG audio tracks. Even though PAL video format has a lower display frame rate,
because of its higher picture resolution, the video contents almost always takes more
storage space than what would require for the equivalent the NTSC version.

Home Theatre Troubleshooting - 2007

Dolby Digital Audio

Dolby Digital soundtracks are very popular with many commercial DVD-Video releases. However, the
DVD specification does not require that the soundtrack have to be Dolby Digital. There are other formats
such as MPEG audio, PCM audio, and DTS. Dolby Digital, DTS, and MPEG audio record audio samples
in compressed format while PCM audio samples are uncompressed.

The full name of Dolby Digital or AC-3 is Dolby Di gital 5.1. The name describes the sound distribution
on six channels in space. All the six channels are compressed into one stereo file, which is unpacked
with a special decoder and divided into six audio columns. According to the AC-3 format the sound is
heard from five wide-band columns: left, right, rear left, rear right, central and from one narrow band,
which is used for low frequency effects (LFE) only. This LFE effect is better felt than heard in the movie
theatres. The number 5.1 indicates five general channels and one LFE channel. Dolby Digital is a great
step forward comparing to Dolby Surround, concerning perception of the spatial sound. The following
illustration shows an ideal setting to enjoy
Dolby Digital soundtracks.

The Dolby Digital format supports soundtracks
in a variety of formats such as mono, dual
mono, stereo, Dolby Surround stereo, Dolby
Surround 5.1 (also commonly known as AC-3).
DVDs with DTS audio soundtracks are required
to include a Dolby Digital audio track. Each DVD
disc can have up to 8 different soundtracks.
Commercial NTSC DVD-Video usually contains
the first soundtrack in Dolby Surround 5.1
and the secondary soundtrack in Dolby Digital Stereo.

Home Theatre Troubleshooting - 2007

Some DVD packaging has small letters or icons under the Dolby Digital logo that indicates the channel configuration.
In many cases, there are often more than one Dolby Digital version of a soundtrack: a 5.1-channel track, and a track

remixed for stereo Dolby Surround. Your DVD player may indicate the playback of a Dolby Digital audio track while
your receiver indicates Dolby Surround. This simply means that the DVD disc contains a two-channel Dolby Surround
signal encoded in Dolby Digital format.

Each DVD disc contains many segments of video and audio contents organized as
chapters in separate video titles. The author of the disc may add optional
navigation commands to skip certain chapters or titles on the DVD. The author

can prohibit access to certain program material on the disc so that one or more
segments of the disc cannot be
seen or played back without
some means of human

intervention. In this case,

it is difficult oreven not possible

to access these hidden contents

from a stand-alone DVD player.

However, most DVD backup software
can display the entire contents of the
DVD so the user can select which
chapter or title to back up. The
hidden portions of the disc by
restricting access with DVD
navigation commands can then
be displayed on the computer
and backed up accordingly. The
navigation commands which skip
the display of these hidden contents
can be removed or modified so that
a standard DVD player may gain
access to these portions via the
menu or the remote control buttons.

Home Theatre Troubleshooting - 2007

DIVX
DivX® is a technol ogy to compress and playback video files. DivXNetworks creates and distributes
this technology which is often referred to as the "MP3 of video". In a nutshell, DivX® has revolutionized
the creation, playback and distribution of high-quality digital video.

DivX® has become the most popular MPEG-4 compatible video compression technology on the
market due to its very high compression ratio which enables DVD-quality video and audio at typically
7-10 times smaller storage requirements than standard DVD/Mpeg2 compression technology.
A commercial DVD title which takes 4.7 gigabytes of storage can be converted to DivX® format with
no noticeable loss of video and audio quality within less than 700 megabytes of storage which can be
archived on cheap CD media. DivX® tech nology allows broadband users to encode and distribute
DVD-quality video at 500-700 Kbps. According to Viant Research, there are over half a million DivX®
video files traded daily on the Internet.

On the down side, DivX® movies are not compatible with DVD technology in the sense that all interactions
that require DVD commands are lost after the conversion. DVD menu presentation, title and chapter
selection, angle selection, etc. are not available with DivX® technology.

The following are some highlights of the DivX® video technology:
Video file format: Most common form as a Windows .avi file
Video Resolution: Variable, 640x480 is the most common or default PAL/NTSC resolution
Bit rate: Varies depending on the video resolution and the audio bit rate. 650 MB typically stores 80-90
minutes at 640x480

Video Quality: Varies depending upon compression parameters. Most common quality is

SVHS/DVD at 10-15% the storage requirements by DVD technology.

Audio Quality: Most common is CD Quality or better at 48 kHz or 96 kBits,

2-channel stereo.

Encoding time: 18-20 frames per second on a P3-1GHz.

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WMA
The Advanced Systems Format (ASF) is the file format used by Windows Media. Audio and/or Video content
compressed with a wide variety of codecs can be stored in an ASF file and played back with the Windows Media
Player (provided the appropriate codecs are installed), streamed with Windows Media Services or optionally
packaged with Windows Media Rights Manager.

ASF is an extensible file format designed to store synchronized multimedia data. It supports data delivery over
a wide variety of networks and protocols while still proving suitable for local playback. ASF supports advanced
multimedia capabilities including extensible media types, component download, scaleable media

(((XM))) READY
Of course, XM Connect & Play compatibility is only one of many reasons to choose a new LG receiver for your home

theater. The new XM-R ead y re cei vers incorporate LG's Digital TOP-ART circuit design concept for crystal-clear sonic

reproduction; a full complement of built-in surround decoders, augmented by LG's proprietary THS processing for

incredible cinematic realism; high-bandwidth component video pass-through for compatibility with 1080i and 720p
video sources; and a host of other advanced and proprietary technologies that make LG the perennial choice of true
home theater enthusiasts. When you think about it, it's a perfect fit: XM's superior, CD-quality broadcast fidelity and
mind-expanding variety is a great match for a high-end home entertainment system with one of these state-of-the-art
receivers at its center.

MADE FOR IPOD
The LHT754 iPOD Dock lets you connect your iPod to this receiver. You can listen to your iPod music and watch iPod

images and movies on your monitor via the receiver. You can also operate your iPod via the receiver’s remote unit with

the On-Screen Display and charge your iPod. Works with iPod nano, iPod mini and iPod .

PLAYS WINDOWS MEDIA
Consumer Electronic Devices (Including but not limited to: digital audio players, car stereos, home stereos, and
consumer Internet appliances)
All consumer electronic devices must meet the criteria below to qualify for the Logo:

Product utilizes a Microsoft Windows Media codec (i.e., Windows Media Audio, Windows Media Video) pursuant to a
Microsoft OEM License Agreement for Embedded Windows Media (or subsequent Windows Media license agreement
from Microsoft).

Home Theatre Troubleshooting - 2007