Service Manuals, User Guides, Schematic Diagrams or docs for : LG Video LV3765 lv_3765_101
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SECTION1 SUMMARY
KEY TO ABBREVIATIONS
A AC :Alternating Current LPF :Low Pass Filter
ACC :Automatic Color Control M MAX :Maximum
ACSS :Automatic Channel Setting System MD :Modulator
ADJ :Adjust MECHA.CTL :Mechanism Control
A/E :Audio Erase MIC :Microphone
AFC :Automatic Frequency Control MIN :Minimum
AFT :Automatic Fine Tuning MIX :Mixer, Mixing
AGC :Automatic Gain Control M.M. :Monostable, Multivibrator
A.H.SW :Audio Head Switch MMV :Mono Multi Vibrator
ALC :Automatic Level Control MOD :Modulation, Modulator
AM :Amplitude Modulation MODEM :Modulator-Demodulator
AMP :Amplifier MPX :Multiplex
ANT :Antenna
N NR :Noise Reduction
APC :Automatic Phase Control
ASS'Y :Assembly O OSC :Oscillator
AUX :Auxiliary OSD :On Screen Display
B B :Base P PB :Playback
BGP :Burst Gate Pulse PCB :Printed Circuit Board
BPF :Bandpass Filter P.CTL :Power Control
BS :Brodcasting Satellite PRE-AMP :Preamplifier
BW or B/W :Black and White P.F :Power Failure
C C :Capacitor, Chroma, Collector PG :Pulse Generator
CAN :Cancel PLL :Phase Locked Loop
CAP :Capstan PREM.DET :Premire Detect
CAP.BRK :Capstan Brake P.P :Peak-to-Peak
CAP.RVS :Capstan Reverse PS :Phase Shift
CATV :Cable Television PWM :Pulse Width Modulation
CBA :Circuit Board Assembly PWR CTL :Power Control
CCD :Charge Coupled Device Q Q :Transistor
C.CTL :Chro Control, Capstan Control QH :Quasi Horizontal
CFG :Capstan Frequency Generator QSR :Quick Setting Record
CHROMA :Chrominance QTR :Quick Timer Record
CNR :Chroma Noise Redution QV :Quasi Vertical
COMB :Combination R R :Resistor, Right
Comb Filter RE(or RC) :Remocon, Receiver
COMP :Comparator REC :Recording
Composite REC S `H' :Record Start `Hight'
Compensation REF :Reference
CONV :Converter REG :Regulated, Regulator
C.ROT SW :Color Rotary Switch REMOCON :Remote Control(unit)
CS :Chip Selcet RF :Radio Frequency
C.SYNC :Composite Synchronization R/P :Record/Playback
CTL DIV :Control Divide RTC :Reel Time Counter
CUR :Current
CYL :Cylinder S S :Serial
S.ACCEL :Slow Accel
D D :Drum, Digital, Diode, Drain SAOP :Second Audio Program
D.ADJ :Drum Adjust SC :Scart, Simulcast
DC :Direct Current S.DET :Secam Detect
D.CTL :Drum Control
SH :Shift
DEMOD :Demodulator
SHARP :Sharpness
DET :Detector
SIF :Sound Intermediate Frequency
DEV :Deviation
SLD :Side Locking
DHP :Double High Pass
S/N :Signal to Noise Ratio
DIGITRON :Digital Display Tube
SP :Standard Play
DL :Delay line
ST :Stereo
DOC :Drop Out Compensator
SUB :Subtract, Subcarrier
DUB :Dubbing
SW or S/W :Switch
D.V SYNC :Dummy Vertical Synchronization
SYNC :Synchronization
E E :Emitter SYSCON :System Control
EE :Electric to Eletric
T T :Coil
EMPH :Emphasis
TP :Test Point
ENA :Enable
TR :Transistor
ENV :Envelope
TRK :Tracking
EP :Extended Play
TRANS :Transformer
EQ :Equalizer
TU :Tuner, Take-up
EXP :Expander
U UHF :Ultra High Frequency
F F :Fuse
FB :Feed Back UNREG :Unregulated
FBC :Feed Back Clamp V V :Volt, Vertical
FE :Full Erase VA :Always Voltage
FG :Frequency Generator VCO :Voltage Controlled Oscillator
FL :Filter VGC :Voltage Gain Control
FM :Frequency Modulation VHF :Very High Frequency
F/R :Front/Rear V.H.SW :Video Head Switch
FS :Frequency Synthesizer VISS :VHS Index Search
FSC :Subcarrier Frequency VPS :Video Program System
F/V :Frequency Voltage VR :Variable Resistor or Volume
G GEN :Generator V-SYNC :Vertical Synchronization
VTG :Voltage
H H :High, Horizontal
VV :Voltage to Voltage
I IC :Integrated Circuit VXO :Voltage X-tal Oscillator
IF :Intermediate Frequency
W W :Watt
INS :Insert
WHT :White
L L :Low, Left, Coil W/O :With out
LD :LED
X X-TAL :Crystal
LD VTG CTL :Loading Voltage Control
LECHA :Letter Character Y Y/C :Luminance/Chrominance
L.M :Level Meter YNR :Luminance Noise Reduction
LP :Long Play Z ZD :Zener Diode
1-1
PRODUCT SAFETY SERVICING GUIDELINES FOR VIDEO PRODUCTS
IMPORTANT SAFETY NOTICE A.C. Voltmeter
This manual was prepared for use only by properly trained audio-video service
technicians.
When servicing this product, under no circumstances should the original
design be modified or altered without permission from LG Electronics
Corporation. All components should be replaced only with types identical to
those in the original circuit and their physical location, wiring and lead dress
must conform to original layout upon completion of repairs.
0.15uF
Special components are also used to prevent x-radiation, shock and fire haz- Place this probe
Good Earth Ground
ard. These components are indicated by the letter "x" included in their compo- such as the Water
on each exposed
nent designators and are required to maintain safe performance. No deviations 1500 OHM metal part.
Pipe, Conduit, etc.
are allowed without prior approval by LG Electronics Corporation.
Circuit diagrams may occasionally differ from the actual circuit used. This way, 10 WATT
implementation of the latest safety and performance improvement changes X-RADIATION
into the set is not delayed until the new service literature is printed.
1. Be sure procedures and instructions to all service personnel cover the sub-
CAUTION: Do not attempt to modify this product in any way. Never perform
ject of x-radiation. The only potential source of x-rays in current TV receivers
customized installations without manufacturer's approval. Unauthorized modi-
is the picture tube. However, this tube does not emit x-rays when the HV is
fications will not only void the warranty, but may lead to property damage or
at the factory-specified level. The proper value is given in the applicable
user injury.
schematic. Operation at higher voltages may cause a failure of the picture
Service work should be performed only after you are thoroughly familiar with tube or high-voltage supply and, under certain circumstances may produce
these safety checks and servicing guidelines. radiation in excess of desirable levels.
GRAPHIC SYMBOLS 2. Only factory-specified CRT anode connectors must be used.
The exclamation point within an equilateral triangle is intended to 3. It is essential that the service personnel have available an accurate and reli-
alert the service personnel to important safety information in the able high-voltage meter.
service literature.
4. When the high-voltage circuitry is operating properly, there is no possibility
The lightning flash with arrowhead symbol within an equilateral tri- of an x-radiation problem. Every time a chassis is serviced, the brightness
angle is intended to alert the service personnel to the presence of should be run up and down while monitoring the high voltage with a meter,
noninsulated "dangerous voltage" that may be of sufficient magni- to be certain that the high voltage does not exceed the specified value and
tude to constitute a risk of electric shock. that it is regulating correctly.
The pictorial representation of a fuse and its rating within an equi- 5. When troubleshooting and making test measurements in a product with a
lateral triangle is intended to convey to the service personnel the problem of excessively high voltage, avoid being unnecessarily close to the
following fuse replacement caution notice: picture tube and the high voltage power supply. Do not operate the product
CAUTION: FOR CONTINUED PROTECTION AGAINST RISK longer than necessary to locate the cause of excessive voltage.
OF FIRE, REPLACE ALL FUSES WITH THE SAME TYPE AND 6. Refer to the CRT Anode High Voltage Measurement and Shutdown
RATING AS MARKED NEAR EACH FUSE. Adjustment procedures described in the appropriate text (where used).
SERVICE INFORMATION IMPLOSION
While servicing, use an isolation transformer for protection from AC line shock. 1. All direct view picture tubes are equipped with an integral implosion protec-
After the original service problem has been corrected, make a check of the fol- tion system; take care to avoid damage during installation.
lowing:
2. Use only the recommended factory replacement tubes.
FIRE AND SHOCK HAZARD
TIPS ON PROPER INSTALLATION
1. Be sure that all components are positioned to avoid a possibility of adjacent
1. Never install any receiver in a closed-in recess, cubbyhole, or closely fitting
component shorts. This is especially important on items trans-ported to and
shelf space over, or close to, a heat duct, or in the path of heated air flow.
from the repair shop.
2. Avoid conditions of high humidity such as: outdoor patio installations where
2. Verify that all protective devices such as insulators, barriers, covers, shields, dew is a factor, near steam radiators where steam leakage is a factor, etc.
strain reliefs, power supply cords, and other hardware have been reinstalled
per the original design. Be sure that the safety purpose of the polarized line 3. Avoid placement where draperies may obstruct venting. The customer
plug has not been defeated. should also avoid the use of decorative scarves or other coverings that
might obstruct ventilation.
3. Soldering must be inspected to discover possible cold solder joints, solder
splashes, or sharp solder points. Be certain to remove all loose foreign par- 4. Wall- and shelf-mounted installations using a commercial mounting kit must
ticles. follow the factory-approved mounting instructions. A product mounted to a
shelf or platform must retain its original feet (or the equivalent thickness in
4. Check for physical evidence of damage or deterioration to parts and compo-
spacers) to provide adequate air flow across the bottom. Bolts or screws
nents, for frayed leads or damaged insulation (including the AC cord), and
used for fasteners must not touch any parts or wiring. Perform leakage tests
replace if necessary.
on customized installations.
5. No lead or component should touch a high current device or a resistor rated
5. Caution customers against mounting a product on a sloping shelf or in a tilt-
at 1 watt or more. Lead tension around protruding metal surfaces must be
ed position, unless the receiver is properly secured.
avoided.
6. A product on a roll-about cart should be stable in its mounting to the cart.
6. After reassembly of the set, always perform an AC leakage test on all
Caution the customer on the hazards of trying to roll a cart with small cast-
exposed metallic parts of the cabinet (the channel selector knobs, antenna
ers across thresholds or deep pile carpets.
terminals, handle and screws) to be sure that set is safe to operate without
danger of electrical shock. DO NOT USE A LINE ISOLATION TRANS- 7. Caution customers against using a cart or stand that has not been listed by
FORMER DURING THIS TEST. Use an AC voltmeter having 5000 ohms per Underwriters Laboratories, Inc. for use with its specific model of television
volt or more sensitivity in the following manner: Connect a 1500 ohm, 10 receiver or generically approved for use with TVs of the same or larger
watt resistor, paralleled by a .15 mfd 150V AC type capacitor between a screen size.
known good earth ground water pipe, conduit, etc.) and the exposed metal- 8. Caution customers against using extension cords. Explain that a forest of
lic parts, one at a time. Measure the AC voltage across the combination of extensions, sprouting from a single outlet, can lead to disastrous conse-
1500 ohm resistor and .15 mfd capacitor. Reverse the AC plug by using a quences to home and family.
non-polarized adaptor and repeat AC voltage measurements for each
exposed metallic part. Voltage measured must not exceed 0.75 volts RMS.
This corresponds to 0.5 milliamp AC. Any value exceeding this limit consti-
tutes a potential shock hazard and must be corrected immediately.
1-2
SERVICING PRECAUTIONS
CAUTION : Before servicing the VCR covered by this service Electrostatically Sensitive (ES) Devices
data and its supplements and ADDENDUMS, read and fol- Some semiconductor (solid state) devices can be damaged
low the SAFETY PRECAUTIONS. NOTE : if unforeseen cir- easily by static electricity. Such components commonly are
cumstances create conflict between the following servicing called Electrostatically Sensitive (ES) Devices. Examples of
precautions and any of the safety precautions in this publi- typical ES devices are integrated circuits and some field
cations, always follow the safety precautions. effect transistors and semiconductor chip components.
Remember Safety First: The following techniques should be used to help reduce the
incidence of component damage caused by static electricity.
General Servicing Precautions
1. Always unplug the VCR AC power cord from the AC 1. Immediately before handling any semiconductor compo-
power source before: nent or semiconductor-equipped assembly, drain off any
(1) Removing or reinstalling any component, circuit board, electrostatic charge on your body by touching a known
module, or any other assembly. earth ground. Alternatively, obtain and wear a commer-
(2) Disconnection or reconnecting any internal electrical cially available discharging wrist strap device, which
plug or other electrical connection. should be removed for potential shock reasons prior to
(3) Connecting a test substitute in parallel with an elec- applying power to the unit under test.
trolytic capacitor.
Caution : A wrong part substitution or incorrect 2. After removing an electrical assembly equipped with ES
polarity installation of electrolytic capacitors may result devices, place the assembly on a conductive surface such
in an explosion hazard. as aluminum foil, to prevent electrostatic charge buildup or
exposure of the assembly.
2. Do not spray chemicals on or near this VCR or any of
its assemblies. 3. Use only a GROUNDED-tip soldering iron to solder or
unsolder ES devices.
3. Unless specified otherwise in this service data, clean
electrical contacts by applying an appropriate contact 4. Use only an anti-static solder removal device. Some
cleaning solution to the contacts with a pipe cleaner, solder removal devices not classified a "anti-static" can
cotton-tipped swab, or comparable soft applicator. generate electrical charges sufficient to damage ES
Unless specified otherwise in this service data, lubrication devices.
of contacts is not required.
5. Do not use freon-propelled chemicals. These can
4. Do not defeat any plug/socket B+ voltage interlocks with generate electrical charge sufficient to damage ES
whitch instruments covered by this service manual might devices.
be equipped.
6. Do not remove a replacement ES device from its protec
5. Do not apply AC power to this VCR and/or any of its tive package until immediately before you are ready to
electrical assemblies unless all solid-state device heat install it. (Most replacement ES devices are packaged with
sinks are cerrectly installed. leads electrically shorted together by conductive foam,
aluminum foil, or comparable conductive material).
6. Always connect test instrument ground lead to the
appropriate ground before connection the test instrument
positive lead. Always remove the test instrument ground 7. Immediately before removing the protective material from
lead last. the leads of a replacement ES device, touch the protective
material to the chassis or circuit assembly into which the
Insulation Checking Procedure device will be installed.
Disconnect the attachment plug from the AC outlet and turn
the power on. Connect an insulation resistance meter(500V) Caution : Be sure no power is applied to the chassis or
to the blades of the attachment plug. The insulation resis- circuit, and observe all other safety precautions.
tance between each blade of the attachment plug and acces-
sible conductive parts (Note 1) should be more than 1M- 8. Minimize bodily motions when handling unpackaged
ohm. replacement ES devices. (Normally harmless motion such
Note 1 : Accessible Conductive Parts including Metal pan- as the brushing together of your clothes fabric or the lifting
els, Input terminals, Earphone jacks, etc. of your foot from a carpeted floor can generate static elec-
tricity sufficient to damage an ES device.)
1-3
PROPOSAL FOR APPLYING SHORT PROTECTION
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