Panasonic PT- 47WX49E Service Manual

Also see for PT- 47WX49E: Schematic Notes

Contents

- 2 -Service ManualImportant Safety NoticeSpecial components are used in this projection television that are important for safety. These components areidentified on the schematic diagram by the symbol and printed in BOLD TYPE on the replacement part list. It isessential that these critical parts be replaced with the manufacturer’s specified replacement part to prevent x-rayradiation, shock, fire or other hazards. Do not modify the original design without the manufacturer’s permission.Safety PrecautionsGeneral GuidelinesAnisolation transformer should always be usedduring the servicing of a PTV whose chassis is notisolated from AC power line. Use a transformer ofadequate power rating as this protects the technicianfrom accidents resulting in personal injury fromelectrical shocks. It will also protect the PTV from beingdamaged by accidental shorting that may occurduring servicing.When servicing, observe the original lead dress,especially in the high voltage circuit. Replace alldamaged parts (also parts that show signs ofoverheating.)Always replace protective devices, such asfishpaper, isolation resistors and capacitors, andshields after servicing the PTV. Use onlymanufacturer’s recommended rating for fuses, circuits’breakers, etc.High potentials, as high as 32kV, are present when thisPTV is operating. Operation of the PTV without the rearcover introduces danger for electrical shock. Servicingshould not be performed by anyone who is notthoroughly familiar with the necessary precautionswhen servicing high-voltage equipment.Extreme care should be practiced when handling thepicture tube. Rough handling may cause it to implodedue to atmospheric pressure. (14.7 lbs. per sq. in.). Donot nick or scratch the glass or subject it to any unduepressure. When handling, use safety goggles andheavy gloves for protection. Discharge the picturetube by shorting the anode to chassis ground (not tothe cabinet or to other mounting hardware). Whendischarging, connect cold ground (i.e. DAG groundlead) to the anode with a well-insulated wire or use agrounding probe.X-ray PrecautionsThe front area (between the projection tube and thelens) is enclosed by a metal box to ensure positivesafety during normal and abnormal conditions whenchecking and repairing. To fully ensure safety, thefollowing precautions must be observed.1. Do not remove the lens or metal box.2. Make sure to turn the power OFF when the lens isremoved or when checking the cleanliness of thelens.3. Do not remove the lens or metal box to check theprojection tube for operation by watching it directly.Use a mirror or paper to view the image.Before returning a serviced PTV to the owner, theservice technician must thoroughly test the unit toensure that is completely safe to operate. Do not use aline isolation transformer when testing.Leakage Current Cold CheckUnplug the AC cord and connect a jumper between thetwo plug prongs. Press the POWER switch ON.Measure the resistance between the jumpered AC plugand expose metallic parts such as screw heads,antenna terminals, control shafts, etc. If the exposedmetallic part has a return path to the chassis, thereading should be between 240kW and 5.2MW. If theexposed metallic part does not have a return path tothe chassis, the reading should be infinite.Leakage Current Hot Check (See Fig. 1)Plug the AC cord directly into the AC outlet. Do not usean isolation transformer during the check.Connect a 1.5kW 10-watt resistor in parallel with a0.15mF capacitor between and exposed metallic partand ground. Use earth ground, for example a waterpipe.Using a DVM with a 1000 ohms/volt sensitivity orhigher, measure the AC potential across the resistor.Repeat the procedure and measure the voltagepresent with all other expose metallic parts.Verify any potential does not exceed 0.75 volt RMS. Aleakage current tester (such a Simpson Model 229,Sencore Model PR57 or equivalent) may be used inthe above procedure, in which case any currentmeasure must not exceed 0.5 milliamp. If anymeasurement is out of the specified limits, there is apossibility of a shock hazard and the PTV must berepaired and rechecked before it is returned to thecustomer.Insulation TestConnect an insulation tester between an exposedmetallic part and AC line.Apply 1080VAC/60Hz for 1 second. Confirm that thecurrent measurement is 0.5mA ~ 2.0mA. Repeat testwith other metallic exposed parts.X-ray RadiationWARNING: The potential source of X-ray radiation in thePTV is in the high voltage section and the picture tube.Note: It is important to use calibrated equipment.Apply all black video signals (1080i) and confirm highvoltage measures 31.5 ± 1.0kV. If the high voltage isnot within the range, change C514 to 1800pF, 2000pF,2400pF or 2700pF until the desired value is obtained.Apply NTSC Lion Head Pattern and confirm the highvoltage measures 30.1 ± 1.5kV.Apply HD 1081I Monoscope Pattern and confirm thehigh voltage measures 30.1 ± 1.5kVFigure 1. Hot Check Circuit