Philips-MX-975-D-Service-Manual(1) 电路图 维修手册.pdf

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1、Color TelevisionChassis FR970/17 1931 Service Service Service ServiceManual ContentsContents 4. Mechanical Instructions00 6. Block Diagrams and Testpoints00 7. Electrical Diagrams and PWBsDiagramPWB WIRING DIAGRAM1 0 FRONT PANEL leakage current must not exceed 0.5milliamp. If a measurement is outsid

2、e of the specified limits, there is a possibility of shock hazard. The receiver should be repaired and rechecked before returning it to the customer. 5. Repeat the above procedure with the ac plug reversed. (Note: An ac adapter is necessary when a polarized plug is used. Do not defeat the polarizing

3、 feature of the plug.) OR With the instrument completely reassembled, plug the AC line cord directly into a 120V AC outlet. (Do not use an isolation transformer during this test.) Use a leakage current tester or a metering system that complies with American National Standards Institute (ANSI) C101.1

4、 Leakage Current for Appliances and Underwriters Laboratories (UL) 1410, (50.7). With the instrument AC switch first in the on position and then in the off position, measure from a known earth ground (metal water pipe, conduit, etc.) to all exposed metal parts of the instrument (antennas, handle bra

5、ckets, metal cabinet, screw heads, metallic overlays, control shafts, etc.), especially any exposed metal parts that offer an electrical return path to the chassis. Any current measured must not exceed 0.5 milliamp. Reverse the instrument power cord plug in the outlet and repeat the test. See graphi

6、c below. PICTURE TUBE REPLACEMENT The primary source of X-radiation in this television receiver is the picture tube. The picture tube utilized in this chassis is specially constructed to limit X-radiation emissions. For continued X-radiation protection, the replacement tube must be the same type as

7、the original, including suffix letter, or a Philips approved type. PARTS REPLACEMENT Many 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 by them

8、 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 Philips recommended replacement part shown in this service manual may create shock, fire, or other hazards TV SAFET

9、Y NOTES SAFETY CHECKS IMPLOSION X-RADIATION PICTURE TUBE REPLACEMENT PARTS REPLACEMENT WARNING Before removing the CRT anode cap, turn the unit OFF and short the HIGH VOLTAGE to the CRT DAG ground. SERVICE NOTE: The CRT DAG is not at chassis ground. TV-VCR COMBI SAFETY NOTES IMPORTANT SAFETY PRECAUT

10、IONS Prior to shipment from the factory, our products are strictly inspected for recognized product safety and electrical codes of the countries in which they are to be sold. However, in order to maintain such compliance, it is equally important to implement the following precautions when a set is b

11、eing serviced. SAFETY PRECAUTIONS FOR TV CIRCUITS 1. 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 serv

12、icing. (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 i

13、n place all protective devices, including but not limited to, nonmetallic control knobs, insulating fishpapers, adjustment and compartment covers/shields, and isolation resistor/capacitor networks. Do not operate this instrument or permit it to be operated without all protective devices correctly in

14、stalled and functioning. Servicers who defeat safety features or fail to perform safety checks may be liable for any resulting damage. b. Be sure that there are no cabinet openings through which an adult or child might be able to insert their fingers and contact a hazardous voltage. Such openings in

15、clude, 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

16、INDICATE A POTENTIAL SHOCK HAZARD THAT MUST BE ELIMINATED BEFORE RETURNING THE INSTRUMENT TO THE CUSTOMER OR BEFORE CONNECTING THE ANTENNA OR ACCESSORIES. d. X-Radiation and High Voltage Limits - Because the picture tube is the primary potential source of X-radiation in solid-state TV receivers, it

17、is specially constructed to prohibit X-radiation emissions. For continued X-radiation protection, the replacement picture tube must be the same type as the original. Also, because the picture tube shields and mounting hardware perform an X-radiation protection function, they must be correctly in pla

18、ce. High voltage must be measured each time servicing is performed that involves B+, horizontal deflection or high voltage. Correct operation of the X-radiation protection circuits also must be reconfirmed each time they are serviced. (X-radiation protection circuits also may be called horizontal di

19、sable or hold down.) Read and apply the high voltage limits and, if the chassis is so equipped, the X-radiation protection circuit specifications given on instrument labels and in the Product Safety because of potential hazard, do not try to remove such permanently attached yokes from the picture tu

20、be. 5. Hot Chassis Warning a. Some TV receiver chassis are electrically connected directly to one conductor of the ac power cord and may be serviced safely without an isolation transformer only if the ac power plug is inserted so that the chassis is connected to the ground side of the ac power sourc

21、e. To confirm that the ac power plug is inserted correctly, with an ac voltmeter, measure between the chassis and a known earth ground. If a voltage reading in excess of 1.OV is obtained, remove and reinsert the ac power plug in the opposite polarity and again measure the voltage potential between t

22、he chassis and a known earth ground. b. Some TV receiver chassis normally have 85Vac (RMS) between chassis and earth ground regardless of the ac plug polarity. This chassis can be safety-serviced only with an isolation transformer inserted in the power line between the receiver and the ac power sour

23、ce, for both personnel and test equipment protection. Some TV receiver chassis have a secondary ground system in addition to the main chassis ground. This secondary ground system is not isolated from the ac power line. The two ground systems are electrically separated by insulation material that mus

24、t 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 touch thermally hot parts, c. the ac supply, d. high voltage, and e. antenna

25、wiring. Always inspect in all areas for 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 should be replaced with components, parts, or wiring that meet original specifications. Additio

26、nally, determine the cause of overheating and/or damage and, if necessary, take corrective action to remove any potential safety hazard. PRECAUTIONS DURING SERVICE A. Parts identified by the symbol are critical for safety. Replace only with part number specified. B. In addition to safety, other part

27、s and assemblies are specified for conformance with regulations applying 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 especia

28、lly: 1) Wires covered with PVC tubing 2) Double insulated wires 3) High voltage leads D. Use specified insulating materials for hazardous live parts. Note especially: 1) Insulation Tape 2) PVC tubing 3) Spacers 4) Insulators for transistors E. When replacing ac primary side components (transformers,

29、 power cord, etc.), wrap ends of wires securely 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 pow

30、er cord has been replaced, check that 10-15 kg of force in any direction will not loosen 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 connector When replacing the power transf

31、ormer in sets where the connections between the power cord and power transformer primary lead wires are performed using crimp type connectors, in order to prevent shock hazards, perform carefully and precisely the following steps. Replacement procedure 1) Remove the old connector by cutting the wire

32、s at a point close to the connector. Important: Do not 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, twist the strands to avoid frayed conductors. 3) Align the lengths of the wires to be connected. Insert the wires full

33、y into the connector. 4) Use the crimping tool to crimp the metal sleeve at the center position. Be sure to crimp fully to the complete closure of the tool. L. When connecting or disconnecting the VCR connectors, first, disconnect the ac plug from the ac supply socket. SAFETY CHECK AFTER SERVICING E

34、xamine 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 and confirm the specified values in order to verify compliance with safety standards. 1. Clearance Dis

35、tance When replacing primary circuit components, confirm specified clearance distance (d) and (d) between soldered terminals, and between terminals and surrounding metallic parts. (See graphic bllow) Table 1 : Ratings for selected area AC Line Voltage Region Clearance Distance (d) (d) USA or 3.2 mm

36、110 to 130 V CANADA (0.126 inches) Note: This table is unofficial and for reference only. Be sure to confirm the precise values. 2. LEAKAGE CURRENT CHECKS VCR SAFETY NOTES FIRE & SHOCK HAZARD (VCR) 1. Be sure that all components are positioned in such a way to avoid possibility of shorts to adjacent

37、 components. This is especially important on those chassis which are transported to and from the repair shop. 2. Always replace all protective devices such as insulators and barriers after working on a set. 3. Check for damaged insulation on wires including the ac cord. 4. Check across-the-line comp

38、onents for damage and replace if necessary. 5. After re-assembly of the unit, always perform an ac leakage test on the exposed metallic parts of the cabinet such as the knobs, antenna terminals, etc. to be sure the set is safe to operate without danger of electrical shock. Do not use a line isolatio

39、n transformer during this test. Use an ac voltmeter having 5000 ohms per volt or more sensitivity in the following manner: Connect a 1500 ohm 10 wan resistor, paralleled by 0.15 MFD ac type capacitor, between a known good earth ground (water pipe, conduit, etc.) and the exposed metallic parts, one a

40、t a time. Measure the ac voltage across the combination 1500 ohm resistor and 0.15 MFD capacitor. Reverse the ac plug on the set and repeat ac voltage measurements again for each exposed metallic part. Voltage measured must not exceed O.6 volts R.M.S. This corresponds to 0.4 milliamp ac. Any value e

41、xceeding this limit constitutes a potential shock hazard and must be corrected immediately. GENERAL Power Supply-This receiver is designed for operation on 120 Volts, 6OHz alternating current (ac) only. Never connect to a supply having a different frequency or voltage. IMPORTANT NOTICE This device e

42、mploys many circuits, components, and mechanical parts designed for protection against fire, shock and RF interference. For continued safety any servicing should be performed by qualified personnel and exact replacement parts should be used. Under no circumstances should the original design be alter

43、ed. PRODUCT SAFETY GUIDELINES FOR ALL PRODUCTS CAUTION: Do not modify any circuit. Service work should be performed only after you are thoroughly familiar with all of the following safety checks. Risk of potential hazards and injury to the user increases if safety checks are not adhered to. USE A SE

44、PARATE ISOLATION TRANSFORMER FOR THIS UNIT WHEN SERVICING. PREVENTION OF ELECTROSTATIC DISCHARGE (ESD) 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

45、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 electrostatic discharge (ESD). 1. Immediately before handling any semiconductor component or semiconductor-equip

46、ped assembly, drain off any ESD on your body by touching a known earth ground. Alternatively, obtain and wear a commercially available discharging ESD wrist strap, which should be removed for potential shock reasons prior to applying power to the unit under test. 2. After removing an electrical asse

47、mbly 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 sol

48、der removal devices not classified as antistatic (ESD protected) can generate an electrical charge sufficient to damage ES devices. 5. Do not use freonpropelled chemicals. These can generate electrical charges sufficient to damage ES devices. 6. Do not remove a replacement ES device from its protect

49、ive 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