Philips-MX-975-D-Service-Manual电路原理图.pdf

Color Television ChassisFR970/171931ServiceServiceServiceServiceManualContents Contents4. Mechanical Instructions 00 6. Block Diagrams and Testpoints 00 7. Electrical Diagrams and PWB's Diagram PWBWIRING DIAGRAM 1 0 FRONT PANEL leakage current must not exceed 0.5milliamp. If a measurement is outside of thespecified limits, there is a possibility of shock hazard. The receiver should be repaired and recheckedbefore returning it to the customer.5. Repeat the above procedure with the ac plug reversed. (Note: An ac adapter isnecessary when a polarized plug is used. Do not defeat the polarizing feature of the plug.)ORWith the instrument completely reassembled, plug the AC line cord directly into a 120V AC outlet. (Donot use an isolation transformer during this test.) Use a leakage current tester or ametering system that complies with American National Standards Institute (ANSI) C101.1 LeakageCurrent for Appliances and Underwriters Laboratories (UL) 1410, (50.7). With the instrumentAC switch first in the on position and then in the off position, measure from aknown earth ground (metal water pipe, conduit, etc.) to all exposed metalparts of the instrument (antennas, handle brackets, metal cabinet, screwheads, metallic overlays, control shafts, etc.), especially any exposed metalparts that offer an electrical return path to the chassis. Any currentmeasured must not exceed 0.5 milliamp. Reverse the instrument power cordplug in the outlet and repeat the test. See graphic below.PICTURE TUBE REPLACEMENTThe primary source of X-radiation in this television receiver is the picture tube. The picture tube utilizedin this chassis is specially constructed to limit X-radiation emissions. For continued X-radiationprotection, the replacement tube must be the same type as the original, including suffix letter, or aPhilips approved type.PARTS REPLACEMENTMany electrical and mechanical parts in Philips television sets have special safety related characteristics. These characteristics are often not evident from visual inspection nor can the protection afforded bythem necessarily be obtained by using replacement components rated for higher voltage, wattage, etc. The use of a substitute part which does not have the same safety characteristics as the Philipsrecommended replacement part shown in this service manual may create shock, fire, or other hazardsTV SAFETY NOTESSAFETY CHECKSIMPLOSION X-RADIATIONPICTURE TUBE REPLACEMENT PARTS REPLACEMENT WARNINGBefore removing the CRT anode cap, turn the unit OFF and short the HIGH VOLTAGE to the CRT DAGground.SERVICE NOTE: The CRT DAG is not at chassis ground.TV-VCR COMBI SAFETY NOTESIMPORTANT SAFETY PRECAUTIONSPrior to shipment from the factory, our products are strictly inspected for recognized product safety andelectrical codes of the countries in which they are to be sold. However, in order to maintain suchcompliance, it is equally important to implement the following precautions when a set is being serviced.SAFETY PRECAUTIONS FOR TV CIRCUITS1. Before returning an instrument to the customer, always make a safety check of the entire instrument,including, but not limited to, the following items:a. Be sure that no built-in protective devices are defective or have been defeated during servicing.(1) Protective shields are provided on this chassis to protect both the technician and the customer. Correctly replace all missing protective shields, including any removed for servicing convenience. (2)When reinstalling the chassis and/or other assembly in the cabinet, be sure to put back in place allprotective devices, including but not limited to, nonmetallic control knobs, insulating fishpapers,adjustment and compartment covers/shields, and isolation resistor/capacitor networks. Do notoperate this instrument or permit it to be operated without all protective devices correctly installedand functioning. Servicers who defeat safety features or fail to perform safety checks may be liablefor any resulting damage.b. Be sure that there are no cabinet openings through which an adult or child might be able to inserttheir fingers and contact a hazardous voltage. Such openings include, but are not limited to, (1)spacing between the picture tube and the cabinet mask, (2) excessively wide cabinet ventilation slots,and (3) an improperly fitted and/or incorrectly secured cabinet back cover.c. Do a LEAKAGE CURRENT CHECK ANY MEASUREMENTS NOT WITHIN THE LIMITS SPECIFIED HEREIN INDICATE A POTENTIAL SHOCKHAZARD THAT MUST BE ELIMINATED BEFORE RETURNING THE INSTRUMENT TO THE CUSTOMEROR BEFORE CONNECTING THE ANTENNA OR ACCESSORIES.d. X-Radiation and High Voltage Limits - Because the picture tube is the primary potentialsource of X-radiation in solid-state TV receivers, it is specially constructed to prohibit X-radiationemissions. For continued X-radiation protection, the replacement picture tube must be the same typeas the original. Also, because the picture tube shields and mounting hardware perform an X-radiationprotection function, they must be correctly in place. High voltage must be measured each timeservicing is performed that involves B+, horizontal deflection or high voltage. Correct operation ofthe X-radiation protection circuits also must be reconfirmed each time they are serviced. (X-radiationprotection circuits also may be called “horizontal disable“ or “hold down.“) Read and apply the highvoltage limits and, if the chassis is so equipped, the X-radiation protection circuit specifications givenon instrument labels and in the Product Safety because of potential hazard, do not try to remove such “permanently attached“yokes from the picture tube.5. Hot Chassis Warning a. Some TV receiver chassis are electrically connected directly to one conductor of the ac powercord and may be serviced safely without an isolation transformer only if the ac power plug is insertedso that the chassis is connected to the ground side of the ac power source. To confirm that the acpower plug is inserted correctly, with an ac voltmeter, measure between the chassis and a knownearth ground. If a voltage reading in excess of 1.OV is obtained, remove and reinsert the ac powerplug in the opposite polarity and again measure the voltage potential between the chassis and aknown earth ground.b. Some TV receiver chassis normally have 85Vac (RMS) between chassis and earth groundregardless of the ac plug polarity. This chassis can be safety-serviced only with an isolationtransformer inserted in the power line between the receiver and the ac power source, for bothpersonnel and test equipment protection. Some TV receiver chassis have a secondary groundsystem in addition to the main chassis ground. This secondary ground system is not isolated fromthe ac power line. The two ground systems are electrically separated by insulation material thatmust not be defeated or altered.6. Observe original lead dress. Take extra care to assure correct lead dress in the following areas: a.near sharp edges, b. near thermally hot parts - be sure that leads and components do not touchthermally hot parts, c. the ac supply, d. high voltage, and e. antenna wiring. Always inspect in all areasfor pinched, out of place, or frayed wiring. Check ac power cord for damage.7. Components, parts, and/or wiring that appear to have overheated or are otherwise damaged shouldbe replaced with components, parts, or wiring that meet original specifications. Additionally, determinethe cause of overheating and/or damage and, if necessary, take corrective action to remove anypotential safety hazard.PRECAUTIONS DURING SERVICEA. Parts identified by the symbol are critical for safety. Replace only with part number specified.B. In addition to safety, other parts and assemblies are specified for conformance with regulationsapplying to spurious radiation. These must also be replaced only with specified replacements. Examples: RF converters, RF cables, noise blocking capacitors, and noise blocking filters, etc.C. Use specified internal wiring. Note especially:1) Wires covered with PVC tubing2) Double insulated wires3) High voltage leadsD. Use specified insulating materials for hazardouslive parts. Note especially:1) Insulation Tape2) PVC tubing3) Spacers4) Insulators for transistorsE. When replacing ac primary side components (transformers, power cord, etc.), wrap ends of wiressecurely about the terminals before soldering.F. Observe that the wires do not contact heat producing parts (heatsinks, oxide metal film resistors,fusible resistors, etc.)G. Check that replaced wires do not contact sharp edged or pointed parts.H. When a power cord has been replaced, check that 10-15 kg of force in any direction will notloosen it.I. Also check areas surrounding repaired locations.J. Use care that foreign objects (screws, solder droplets, etc.) do not remain inside the set.K. Crimp type wire connectorWhen replacing the power transformer in sets where the connections between the power cord and powertransformer primary lead wires are performed using crimp type connectors, in order to prevent shockhazards, perform carefully and precisely the following steps.Replacement procedure1) Remove the old connector by cutting the wires at a point close to the connector. Important: Donot re-use a connector (discard it).2) Strip about 15 mm of the insulation from the ends of the wires. If the wires are stranded, twistthe strands to avoid frayed conductors.3) Align the lengths of the wires to be connected. Insert the wires fully into the connector.4) Use the crimping tool to crimp the metal sleeve at the center position. Be sure to crimp fully tothe complete closure of the tool.L. When connecting or disconnecting the VCR connectors, first, disconnect the ac plug from the acsupply socket.SAFETY CHECK AFTER SERVICINGExamine the area surrounding the repaired location for damage or deterioration. Observe that screws,parts and wires have been returned to original positions. Afterwards, perform the following tests andconfirm the specified values in order to verify compliance with safety standards.1. Clearance DistanceWhen replacing primary circuit components, confirm specified clearance distance (d) and (d') betweensoldered terminals, and between terminals and surrounding metallic parts. (See graphic bllow)Table 1 : Ratings for selected areaAC Line Voltage Region Clearance Distance (d) (d')USA or > 3.2 mm110 to 130 V CANADA (0.126 inches)Note: This table is unofficial and for reference only. Be sure to confirm the precise values.