Panasonic TX-21AD2 Service Manual

Also see for TX-21AD2: Operating instructions Service manual

Contents

Panasonic TX-21AD2 Service Manual Manual pdf 2 page image

ContentsSafety Precautions 2Location of Controls 3Chassis Service Position 4Service Mode 5Self Check 6Adjustment Procedure 6Alignment Settings 7Waveform Pattern Table 8Block Diagrams 9P.C.B. Views 12Schematic Diagrams 14Parts Location 17Replacement Parts List 18Safety PrecautionsGeneral Guide Lines1. It is advisable to insert an isolation transformer in the AC supplybefore servicing a hot chassis.2. When servicing, observe the original lead dress in the highvoltage circuits. If a short circuit is found, replace all parts whichhave been overheated or damaged by the short circuit.3. After servicing, see that all the protective devices such asinsulation barriers, insulation papers, shields and isolation R-Ccombinations are correctly installed.4. When the receiver is not being used for a long period of time,unplug the power cord from the AC outlet.5. Potentials as high as 28kV are present when this receiver is inoperation. Operation of the receiver without the rear coverinvolves the danger of a shock hazard from the receiver powersupply. Servicing should not be attempted by anyone who is notfamiliar with the precautions necessary when working on highvoltage equipment. Always discharge the anode of the picture tothe chassis before handling the tube.6. After servicing make the following leakage current checks toprevent the customer from being exposed to shock hazards.Leakage Current Cold Check1. Unplug the AC cord and connect a jumper between the twoprongs of the plug.2. Turn on the receiver's power switch.3. Measure the resistance value with an ohmmeter, between thejumpered AC plug and each exposed metallic cabinet part on thereceiver, such as screw heads, aerials , connectors, controlshafts etc. When the exposed metallic part has a return path tothe chassis the reading should be between 4M ohm and 20Mohm. When the exposed metal does not have a return path tothe chassis the reading must be infinite.Leakage Current Hot Check1. Plug the AC cord directly into the AC outlet. Do not use anisolation transformer for this check.2. Connect a 2k ohm 10W resistor in series with an exposedmetallic part on the receiver and an earth such as a water pipe.3. Use an AC voltmeter with high impedance to measure thepotential across the resistor.4. Check each exposed Metallic part and check the voltage at eachpoint.5. Reverse the AC plug at the outlet andrepeat each of the abovemeasurements.6. The potential at any point should not exceed 1.4Vrms. In case ameasurement is outside the limits specified, there is a possibilityof a shock hazard, and the receiver should be repaired andrechecked before it is returned to the customer.X-Radiation Warning1. The potential sources of X-Radiation in TV sets are the highvoltage section and the picture tube.2. When using a picture tube test jig for service ensure that the jigis capable of handling 28kV without causingX-Radiation.NOTE : It is important to use an accurate periodically calibrated highvoltage meter1. Set the brightness to minimum.2. Measure the high voltage. The meter should indicate 27kV _1kVat zero beam current if the meter indication is out of tolerance,immediate service and correction is required to prevent thepossibility of premature component failure.3. To prevent an X-Radiation possibility, it is essential to use thespecified tube.HOT CHECK CIRCUIT2K ohm 10WA.C. VoltmeterWater Pipe(Earth)To Instrument'sexposedmetallic partsFig.1