Panasonic TC-21P50R Service Manual

Also see for TC-21P50R: Operating instructions

Contents

Panasonic TC-21P50R Service Manual Manual pdf 3 page image

- 3 -Safety PrecautionsGeneral Guide1. It is advisable to insert an isolation transformer in the ACsupply before servicing a hot chassis.2. When servicing, observe the original lead dress, espe-cially the lead dress in the high voltage circuits.If a short circuit is found, replace all parts which havebeen overheated or damaged by the short circuit.3. After servicing, see to it that all the protective devicessuch as insulation barriers, insulation papers, shields,and isolation R-C combinations, are properly installed.4. When the receiver is not to be used for a long period oftime, unplug the power cord from the AC outlet.5. Potential, as high as 29.2 kV, is present when thisreceiver is in operation. Operation of the receiver with-out the rear cover involves the danger of a shock hazardfrom the receiver power supply. Servicing should not beattempted by anyone who is not thoroughly familiar withthe precautions necessary when working on high volt-age equipment. Always discharge the anode of the pic-ture tube to the receiver chassis before handling thetube.6. After servicing make the following leakage currentchecks to prevent the customer from being exposed toshock hazards.Leakage Current Cold Check1. Unplug the AC cord and connect a jumper between thetwo prongs on the plug.2. Turn on the receiver’s power switch.3. Measure the resistance value, with an ohmmeter,between the jumpered AC plug and each exposedmetallic cabinet part on the receiver, such as screwheads, aerials, connectors, control shafts, etc. Whenthe exposed metallic part has a return path to the chas-sis, the reading should be between 4 M and 20 M.When the exposed metal does not have a return path tothe chassis, the reading must beLeakage Current Hot Check1. Plug the AC cord directly into the AC outlet.Do not use an isolation transformer for this check.2. Connect a 2 k, 10W resistor, in series with an exposedmetallic part on the receiver and an earth such as awater pipe.3. Use an AC voltmeter, with high impedance type, to mea-sure the potential across the resistor.4. Check each exposed metallic part, and measure thevoltage at each point.5. Reverse the AC plug in the AC outlet and repeat each ofthe above measurements.6. The potential at any point should not exceed 1.0 V rms.In case a measurement is outside of the limits specified,there is a possibility of a shock hazard, and the receivershould be repaired and rechecked before it is returned tothe customer.Isolation T ransformerpower-onHot - Check CircuitAC VoltmeterWater Pipe(Earth)ToInstrument'sMetallic PartsExposed 2kΩ 10W