Zenith DVB251 Schematic

1-2
CAUTION : DO NOT ATTEMPT TO MODIFY THIS PRODUCT IN ANY WAY, NEVER PERFORM CUSTOMIZED INSTALLATIONS WITHOUT MANUFAC­TURER’S APPROVAL. UNAUTHORIZED MODIFICATIONS WILL NOT ONLY VOID THE WARRANTY, BUT MAY LEAD TO YOUR BEING LIABLE FOR ANY RESULTING PROPERTY DAMAGE OR USER INJURY.
SERVICE WORK SHOULD BE PERFORMED ONLY AFTER YOU ARE THOROUGHLY FAMILIAR WITH ALL OF THE FOLLOWING SAFETY CHECKS AND SERVICING GUIDELINES. TO DO OTHERWISE, INCREASES THE RISK OF POTENTIAL HAZARDS AND INJURY TO THE USER.
WHILE SERVICING, USE AN ISOLATION TRANSFORMER FOR PROTEC­TION FROM A.C. LINE SHOCK.
SAFETY CHECKS
AFTER THE ORIGINAL SERVICE PROBLEM HAS BEEN CORRECTED. A CHECK SHOULD BE MADE OF THE FOLLOWING.
SUBJECT : FIRE & SHOCK HAZARD
1. BE SURE THAT ALL COMPONENTS ARE POSITIONED IN SUCH A WAY AS TO AVOID POSSIBILITY OF ADJACENT COMPONENT SHORTS. THIS IS ESPECIALLY IMPORTANT ON THOSE MODULES WHICH ARE TRANSPORTED TO AND FROM THE REPAIR SHOP.
2. NEVER RELEASE A REPAIR UNLESS ALL PROTECTIVE DEVICES SUCH AS INSULATORS, BARRIERS, COVERS, SHIELDS, STRAIN RELIEFS, POWER SUPPLY CORDS, AND OTHER HARDWARE HAVE BEEN REINSTALLED PER ORIGINAL DESIGN. BE SURE THAT THE SAFETY PURPOSE OF THE POLARIZED LINE PLUG HAS NOT BEEN DEFEATED.
3. SOLDERING MUST BE INSPECTED TO DISCOVER POSSIBLE COLD SOLDER JOINTS, SOLDER SPLASHES OR SHARP SOLDER POINTS. BE CERTAIN TO REMOVE ALL LOOSE FOREIGN PARTICLES.
4. CHECK FOR PHYSICAL EVIDENCE OF DAMAGE OR DETERIORATION TO PARTS AND COMPONENTS, FOR FRAYED LEADS, DAMAGED INSULATION (INCLUDING A.C. CORD), AND REPLACE IF NECESSARY. FOLLOW ORIGINAL LAYOUT, LEAD LENGTH AND DRESS.
5. NO LEAD OR COMPONENT SHOULD TOUCH A RECIVING TUBE OR A RESISTOR RATED AT 1 WATT OR MORE. LEAD TENSION AROUND PROTRUDING METAL SURFACES MUST BE AVOIDED.
6. ALL CRITICAL COMPONENTS SUCH AS FUSES, FLAMEPROOF RESISTORS, CAPACITORS, ETC. MUST BE REPLACED WITH EXACT FACTORY TYPES, DO NOT USE REPLACEMENT COMPONENTS OTHER THAN THOSE SPECIFIED OR MAKE UNRECOMMENDED CIR­CUIT MODIFICATIONS.
7. AFTER RE-ASSEMBLY OF THE SET ALWAYS PERFORM AN A.C. LEAKAGE TEST ON ALL EXPOSED METALLIC PARTS OF THE CABI­NET, (THE CHANNEL SELECTOR KNOB, ANTENNA TERMINALS. HAN­DLE AND SCREWS) TO BE SURE THE SET IS SAFE TO OPERATE WITHOUT DANGER OF ELECTRICAL SHOCK. DO NOT USE A LINE ISOLATION TRANSFORMER DURING THIS TEST USE AN A.C. VOLT­METER, HAVING 5000 OHMS PER VOLT OR MORE SENSITIVITY, IN THE FOLLOWING MANNER; CONNECT A 1500 OHM 10 WATT RESIS­TOR, PARALLELED BY A .15 MFD. 150.V A.C TYPE CAPACITOR BETWEEN A KNOWN GOOD EARTH GROUND (WATER PIPE, CON­DUIT, ETC.) AND THE EXPOSED METALLIC PARTS, ONE AT A TIME. MEASURE THE A.C. VOLTAGE ACROSS THE COMBINATION OF 1500 OHM RESISTOR AND .15 MFD CAPACITOR. REVERSE THE A.C. PLUG AND REPEAT A.C. VOLTAGE MEASUREMENTS FOR EACH EXPOSED METALLIC PART. VOLTAGE MEASURED MUST NOT EXCEED 75 VOLTS R.M.S. THIS CORRESPONDS TO 0.5 MILLIAMP A.C ANY VALUE EXCEEDING THIS LIMIT CONSTITUTES A POTENTIAL SHOCK HAZARD AND MUST BE CORRECTED IMMEDIATELY.
SUBJECT: GRAPHIC SYMBOLS
THE LIGHTNING FLASH WITH APROWHEAD SYMBOL. WITHIN AN EQUILATERAL TRIANGLE, IS INTENDED TO ALERT THE SERVICE PERSONNEL TO THE PRESENCE OF UNINSULATED “DANGEROUS VOLTAGE” THAT MAY BE OF SUFFICIENT MAG­NITUDE TO CONSTITUTE A RISK OF ELECTRIC SHOCK.
THE EXCLAMATION POINT WITHIN AN EQUILATERAL TRIAN­GLE IS INTENDED TO ALERT THE SERVICE PERSONNEL TO THE PRESENCE OF IMPORTANT SAFETY INFORMATION IN SERVICE LITERATURE.
SUBJECT : X-RADIATION
1. BE SURE PROCEDURES AND INSTRUCTIONS TO ALL SERVICE PER­SONNEL COVER THE SUBJECT OF X-RADIATION. THE ONLY POTEN­TIAL SOURCE OF X-RAYS IN CURRENT T.V. RECEIVERS IS THE PIC­TURE TUBE. HOWEVER, THIS TUBE DOES NOT EMIT X-RAYS WHEN THE HIGH VOLTAGE IS AT THE FACTORY SPECIFIED LEVEL. THE PROPER VALUE IS GIVEN IN THE APPLICABLE SCHEMATIC. OPERA­TION AT HIGHER VOLTAGES MAY CAUSE A FAILURE OF THE PIC­TURE TUBE OR HIGH VOLTAGE SUPPLY AND, UNDER CERTAIN CIR­CUMSTANCES, MAY PRODUCE RADIATION IN EXCESS OF DESIR­ABLE LEVELS.
2. ONLY FACTORY SPECIFIED C.R.T. ANODE CONNECTORS MUST BE USED. DEGAUSSING SHIELDS ALSO SERVE AS AN X-RAY SHIELD IN COLOR SETS, ALWAYS RE-INSTALL THEM.
3. IT IS ESSNTIAL THAT SERVICE PERSONNEL HAVE AVAILABLE AN ACCURATE AND RELIABLE HIGH VOLTAGE METER. THE CALIBRA­TION OF THE METER SHOULD BE CHECKED PERIODICALLY AGAINST A REFERENCE STANDARD, SUCH AS THE ONE AVAILABLE AT YOUR DISTRIBUTOR.
4. WHEN THE HIGH VOLTAGE CIRCUITRY IS OPERATING PROPERLY THERE IS NO POSSIBILITY OF AN X-RADIATION PROBLEM. EVERY TIME A COLOR CHASSIS IS SERVICED. THE BRIGHTNESS SHOULD BE RUN UP AND DOWN WHILE MONITORING THE HIGH VOLTAGE WITH A METER TO BE CERTAIN THAT THE HIGH VOLTAGE DOES NOT EXCEED THE SPECIFIED VALUE AND THAT IT IS REGULATING CORRECTLY. WE SUGGEST THAT YOU AND YOUR SERVICE ORGA­NIZATION REVIEW TEST PROCEDURES SO THAT VOLTAGE REGU­LATION IS ALWAYS CHECKED AS A STANDARD SERVICING PROCE­DURE AND THAT THE HIGH VOLTAGE READING BE RECORDED ON EACH CUSTOMER’S INVOICE.
5. WHEN TROUBLESHOOTING AND MAKING TEST MEASUREMENTS IN A PRODUCT WITH A PROBLEM OF EXCESSIVE HIGH VOLTAGE, AVOID BEING UNNECESSARILY CLOSE TO THE PICTURE TUBE AND THE HIGH VOLTAGE SUPPLY. DO NOT OPERATE THE PRODUCT LONGER THAN IT IS NECESSARY TO LOCATE THE CAUSE OF EXCES­SIVE VOLTAGE.
6. REFER TO HV. B+ AND SHUTDOWN ADJUSTMENT PROCEDURES DESCRIBED IN THE APPROPRIATE SCHEMATIC AND DIAGRAMS (WHERE USED).
SUBJECT: IMPLOSION
1. ALL DIRECT VIEWED PICTURE TUBES ARE EQUIPPED WITH AN INTE­GRAL IMPLOSION PROTECTION SYSTEM, BUT CARE SHOULD BE TAKEN TO AVOID DAMAGE DURING INSTALLATION, AVOID SCRATCHING THE TUBE. IF SCRATCHED REPLACE IT.
2. USE ONLY RECOMMENDED FACTORY REPLACEMENT TUBES.
SUBJECT : TIPS ON PROPER INSTALLATION
1. NEVER INSTALL ANY PRODUCT IN A CLOSED-IN RECESS, CUBBY­HOLE OR CLOSELY FITTING SHELF SPACE, OVER OR CLOSE TO HEAT DUCT, OR IN THE PATH OF HEATED AIR FLOW.
2. AVOID CONDITIONS OF HIGH HUMIDITY SUCH AS: OUTDOOR PATIO INSTALLATIONS WHERE DEW IS A FACTOR, NEAR STEAM RADIA­TORS WHERE STEAM LEAKAGE IS A FACTOR, ETC.
3. AVOID PLACEMENT WHERE DRAPERIES MAY OBSTRUCT REAR VENTING. THE CUSTOMER SHOULD ALSO AVOID THE USE OF DEC­ORATIVE SCARVES OR OTHER COVERINGS WHICH MIGHT OBSTRUCT VENTILATION.
4. WALL AND SHELF MOUNTED INSTALLATIONS USING A COMMER­CIAL MOUNTING KIT, MUST FOLLOW THE FACTORY APPROVED MOUNTING INSTRUCTIONS. A PRODUCT MOUNTED TO A SHELF OR PLATFORM MUST RETAIN ITS ORIGINAL FEET (OR THE EQUIVALENT THICKNESS IN SPACERS) TO PROVIDE ADEQUATE AIR FLOW ACROSS THE BOTTOM. BOLTS OR SCREWS USED FOR FASTENERS MUST NOT TOUCH ANY PARTS OR WIRING. PERFORM LEAKAGE TEST ON CUSTOMIZED INSTALLATIONS.
5. CAUTION CUSTOMERS AGAINST THE MOUNTING OF A PRODUCT ON SLOPING SHELF OR A TILTED POSITION, UNLESS THE PRODUCT IS PROPERLY SECURED.
6. A PRODUCT ON A ROLL-ABOUT CART SHOULD BE STABLE ON ITS MOUNTING TO THE CART. CAUTION THE CUSTOMER ON THE HAZ­ARDS OF TRYING TO ROLL A CART WITH SMALL CASTERS ACROSS THRESHOLDS OR DEEP PILE CARPETS.
7. CAUTION CUSTOMERS AGAINST THE USE OF A CART OR STAND WHICH HAS NOT BEEN LISTED BY UNDERWRITERS LABORATORIES, INC. FOR USE WITH THEIR SPECIFIC MODEL OF TELEVISION RECEIVER OR GENERICALLY APPROVED FOR USE WITH T.V.’S OF THE SAME OR LARGER SCREEN SIZE.
8. CAUTION CUSTOMERS AGAINST THE USE OF EXTENSION CORDS. EXPLAIN THAT A FOREST OF EXTENSIONS SPROUTING FROM A SIN­GLE OUTLET CAN LEAD TO DISASTROUS CONSEQUENCES TO HOME AND FAMILY.
PRODUCT SAFETY SERVICING GUIDELINES FOR VIDEO PRODUCTS
A.C. VOLTMETER
GOOD EARTH GROUND SUCH AS THE WATER PIPE. CONDUIT. ETC
PLACE THIS PROBE ON EACH EXPOSED METAL PART
1-3
SERVICING PRECAUTIONS
CAUTION : Before servicing the DVD covered by this service data and its supplements and ADDENDUMS, read and fol­low the SAFETY PRECAUTIONS. NOTE : if unforeseen cir­cumstances create conflict between the following servicing precautions and any of the safety precautions in this publi­cations, always follow the safety precautions.
Remember Safety First:
General Servicing Precautions
1. Always unplug the DVD AC power cord from the AC power source before: (1) Removing or reinstalling any component, circuit board,
module, or any other assembly.
(2) Disconnection or reconnecting any internal electrical
plug or other electrical connection.
(3) Connecting a test substitute in parallel with an elec-
trolytic capacitor. Caution : A wrong part substitution or incorrect polarity installation of electrolytic capacitors may result in an explosion hazard.
2. Do not spray chemicals on or near this DVD or any of its assemblies.
3. Unless specified otherwise in this service data, clean electrical contacts by applying an appropriate contact cleaning solution to the contacts with a pipe cleaner, cotton-tipped swab, or comparable soft applicator. Unless specified otherwise in this service data, lubrication of contacts is not required.
4. Do not defeat any plug/socket B+ voltage interlocks with whitch instruments covered by this service manual might be equipped.
5. Do not apply AC power to this DVD and/or any of its electrical assemblies unless all solid-state device heat sinks are cerrectly installed.
6. Always connect test instrument ground lead to the appropriate ground before connection the test instrument positive lead. Always remove the test instrument ground lead last.
Insulation Checking Procedure
Disconnect the attachment plug from the AC outlet and turn the power on. Connect an insulation resistance meter(500V) to the blades of the attachment plug. The insulation resis­tance between each blade of the attachment plug and acces­sible conductive parts (Note 1) should be more than 1M­ohm. Note 1 : Accessible Conductive Parts including Metal pan­els, Input terminals, Earphone jacks, etc.
Electrostatically Sensitive (ES) Devices
Some semiconductor (solid state) devices can be damaged easily by static electricity. Such components commonly are called Electrostatically Sensitive (ES) Devices. Examples of typical ES devices are integrated circuits and some field effect transistors and semiconductor chip components. The following techniques should be used to help reduce the incidence of component damage caused by static electricity.
1. Immediately before handling any semiconductor compo­nent or semiconductor-equipped assembly, drain off any electrostatic charge on your body by touching a known earth ground. Alternatively, obtain and wear a commer­cially available discharging wrist strap device, which should be removed for potential shock reasons prior to applying power to the unit under test.
2. After removing an electrical assembly equipped with ES devices, place the assembly on a conductive surface such as aluminum foil, to prevent electrostatic charge buildup or exposure of the assembly.
3. Use only a GROUNDED-tip soldering iron to solder or unsolder ES devices.
4. Use only an anti-static solder removal device. Some solder removal devices not classified a “anti-static” can generate electrical charges sufficient to damage ES devices.
5. Do not use freon-propelled chemicals. These can generate electrical charge sufficient to damage ES devices.
6. Do not remove a replacement ES device from its protec tive package until immediately before you are ready to install it. (Most replacement ES devices are packaged with leads electrically shorted together by conductive foam, aluminum foil, or comparable conductive material).
7. Immediately before removing the protective material from the leads of a replacement ES device, touch the protective material to the chassis or circuit assembly into which the device will be installed.
Caution : Be sure no power is applied to the chassis or circuit, and observe all other safety precautions.
8. Minimize bodily motions when handling unpackaged replacement ES devices. (Normally harmless motion such as the brushing together of your clothes fabric or the lifting of your foot from a carpeted floor can generate static elec­tricity sufficient to damage an ES device.)
2-1
SECTION 2
CABINET & MAIN CHASSIS
CONTENTS
EXPLODED VIEWS .....................................................................................................................2-2
1. Cabinet and Main Frame Section ...........................................................................................2-2
2. Deck Mechanism Section........................................................................................................2-3
3. Packing Accessory Section....................................................................................................2-5
2-2
EXPLODED VIEWS
1. Cabinet and Main Frame Section
465
465
250
462
462
300
DIG901
465
261
260
275
463
463
465
463
463
463
A00
A43
A42
A47
A46
A48
A49
283
280
452
452
A
5
4
3
2
1
BCD
2-3
2. Deck Mechanism Section
016
012
012
014
014
009
011
008
432
430
430
430
430
031
001
003
004
026
025
002
414
415
415
413
413
413
414
414
416
032
034
033
035
416
416
416
416
037
030
022
023
021
020
036
A03
A01
A02
A04
038
416
005
005
024
039
039
463
040
040
463
008B
008A
038A
A
5
4
3
2
1
BCD
2-5
3. Packing Accessory Section
BATTERY
808
PACKING SHEET
804
PACKING
803
811
812
OWNER'S MANUAL
PLUG ASS'Y 1WAY(YELLOW)
PLUG ASS'Y 2WAY
810
CABLE SET ASS'Y
801
REMOCON
900
BOX CARTON
802
820
PLUG ASS'Y 1WAY(BLACK)
PACKING
803
806
RF CABLE
3-1
SECTION 3
ELECTRICAL
CONTENTS
ELECTRICAL TROUBLESHOOTING GUIDE......................................................................3-2
1. Power(SMPS) Circuit ...............................................................................................................3-2
2. µ-com Circuit............................................................................................................................3-3
3. MPEG Circuit............................................................................................................................3-6
4. Front Circuit(Digitron & Key) ................................................................................................3-7
5. RF/Servo Circuit ......................................................................................................................3-8
BLOCK DIAGRAMS ..................................................................................................................3-12
1. Overall Block Diagram ..........................................................................................................3-12
2. Power (SMPS) Block Diagram ..............................................................................................3-13
3. RF/CD DSP/DVD DSP/DVD servo Block Diagram ..............................................................3-14
4. Audio Block Diagram ............................................................................................................3-15
5. MPEG Block Diagram...........................................................................................................3-16
CIRCUIT DIAGRAMS................................................................................................................3-17
1. Power (SMPS) Circuit Diagram ............................................................................................3-17
2. DVD DSP Circuit Diagram.....................................................................................................3-19
3. Drive & RF Circuit Diagram ..................................................................................................3-21
4. MPEG Circuit Diagram ..........................................................................................................3-23
WAVEFORMS ...........................................................................................................................3-25
5. Audio DM & 5.1CH Circuit Diagram .....................................................................................3-27
6. TIMER & Key Circuit Diagram ..............................................................................................3-29
7. A/V Circuit Diagram ...............................................................................................................3-31
8. A/V Jack Circuit Diagram......................................................................................................3-33
CIRCUIT VOLTAGE CHART.........................................................................................................3-35
PRINTED CIRCUIT DIAGRAMS ............................................................................................3-39
1. MAIN P.C.BOARD (TOP VIEW)..............................................................................................3-39
2. MAIN P.C.BOARD (BOTTOM VIEW)......................................................................................3-41
3. SMPS P.C.BOARD..................................................................................................................3-43
4. TIMER P.C.BOARD.................................................................................................................3-44
5. KEY P.C.BOARD.....................................................................................................................3-43
3-2
ELECTRICAL TROUBLESHOOTING GUIDE
No 5V_D or 5V_A .
No 5.2VA.
Is 5.2VA section working? (Is the POWER CTL at Pin6 High/low?)
Is oscillation present at the Base of Q108?
Replace Q108.
Check D109, C123, R125, R124.
Replace R102.
Replace BD101.
(Bridge rectifier)
Is R102(R104) normal?
Is about AC 100V applied to
IC101 Pin 3.
Check IC101.
Is 5.2V applied to IC102 Pin 1?
Is there a DC voltage at the
(+) terminal of BD101?
Check R127, 128.
(SHUTDOWN CKT)
1. Power(SMPS) Circuit
No FLD
Is 5.2VA section working?
Replace SMPS trans(T101).
Replace the inferior components.
Are D109, L103 open?
NO
NO
NO
NO
NO
NO
YES
YES
YES
YES
YES
YES
YES
A. B.
NO
NO
3-3
Replace Main B/D
Refer to Front Part
Replace IC503
Reconnect it.
2. µ-COM Circuit
A. No Power
Does Logo appear
on the screen?
Is oscillation of
X501 normal?
Are IC501 Pins 193, 808
and 81 normal?
Do Hello appear at FLD?
Is P3901
connected normally?
Is P3901 Pin 7, 8, 9 normal?
The waveform
on 3, 5, 7 pin of IC503
normal?
Check the oscillation
Check short.
OK
Replace IC501
or IC3F1.
Check power.
(Refer to power)
If power is normal
OK
POWER ON
1
1
YES
YES
YES
NO
YES
YES
YES
A
NO
NO
NO
NO
NO
NONO
YES
A
3-4
B. Audio abnormal
D. Open/Close abnormal
Check the
connection of P3901.
Check IC301 Pins 3, 4.
Check Audio jack.
YES (If OK)
YES
NO
NO
YES
YES (If OK)
YES
YES (If OK)
YES (If OK)
YES (If OK)
Refer to Audio part.
Refer to Decoder part.
Refer to PANTERA part.
Replace B/D.
Check Front.
Reconnect it.
Refer to SERVO part.
Check the connection of MD.
AUDIO ABNORMAL
OPEN/CLOSE ABNORMAL
C. Video abnormal
Check Video jack.
YES (If OK)
YES (If OK)
YES (If OK)
Refer to Video part.
Refer to PANTERA part.
Replace B/D.
VIDEO ABNORMAL
3-5
E. Picture abnormal
Check the disc.
If OK
YES (If OK)
YES (If OK)
Refer to Servo part
Check DSP
Check PANTERA
Replace B/D
PICTURE ABNORMAL
F. Disc Error
Check Disc
YES (If OK)
YES (If OK)
Refer to Servo part
Replace B/D
DISC ERROR
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