Panasonic AG-520VDH Service Manual

Also see for AG520VDH - COMB. DVD/VCR/TV: Operating instructions

Contents

Panasonic AG-520VDH Service Manual Manual pdf 3 page image

1 SAFETY PRECAUTIONS1.1. GENERAL GUIDELINES1. IMPORTANT SAFETY NOTICEThere are special components used in this equipmentwhich are important for safety. These parts are marked byin the Schematic Diagrams, Circuit Board Layout,Exploded Views and Replacement Parts List. It is essentialthat these critical parts should be replaced withmanufacturer’s specified parts to prevent X-RADIATION,shock, fire, or other hazards. Do not modify the originaldesign without permission of manufacturer.2. An Isolation Transformer should always be used during theservicing of Combination DVD VCR whose chassis is notisolated from the AC power line. Use a transformer ofadequate power rating as this protects the technician fromaccidents resulting in personal injury from electrical shocks.It will also protect Combination DVD VCR from beingdamaged by accidental shorting that may occur duringservicing.3. When servicing, observe the original lead dress, especiallythe lead dress in the high voltage circuits. If a short circuit isfound, replace all parts which have been overheated ordamaged by the short circuit.4. After servicing, see to it that all the protective devices suchas insulation barriers, insulation papers, shield, andisolation R-C combinations are properly installed.5. Before turning the receiver on, measure the resistancebetween B+ line and chassis ground. Connect (-) side of anohmmeter to the B+ lines, and (+) side to chassis ground.Each line should have more resistance than specified, asfollows :B+ Line Minimum Resistance130 V 110 Ω (Cold chassis ground)28 V 180 Ω (Cold chassis ground)220 V 1 kΩ (Cold chassis ground)6. When the TV set is not used for a long period of time,unplug the power cord from the AC outlet.7. Potentials, as high as 33.0 kV are present when this TV setis in operation. Operation of the TV set without the rearcover involves the danger of a shock hazard from the TVset power supply. Servicing should not be attempted byanyone who is not thoroughly familiar with the precautionsnecessary when working on high voltage equipment.Always discharge the anode of the picture tube to the CRTground of receiver before handling the tube.8. After servicing make the following leakage current checks toprevent the customer from being exposed to shockhazards.1.2. LEAKAGE CURRENT COLDCHECK1. Unplug the AC cord and connect a jumper between the twoprongs on the plug.2. For physically operated power switches, turn power on.Otherwise skip step 2.3. Measure the resistance value, with an ohmmeter, betweenthe jumpered AC plug and each exposed metallic cabinetpart on the receiver, such as screwheads, connectors, etc.When the exposed metallic part has a return path to thechassis, the reading should be between 1 MΩ and 12 MΩ.When the exposed metal does not have a return path to thechassis, the reading must be infinity.1.3. LEAKAGE CURRENT HOTCHECK1. Plug the AC cord directly into the AC outlet.Do not use a isolation transformer for this check.2. Connect a 1.5 kΩ, 10 W resistor, in parallel with a 0.15 μFcapacitor, between each exposed metallic part on the setand a good earth ground, as shown in Figure 1.3. Use an AC voltmeter, with 1 kΩ/V or more sensitivity, tomeasure 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 of theabove measurements.6. The potential at any point should not exceed 0.75 V RMS.A leakage current tester (Simpson Model 229 equivalent)may be used to make the hot checks. Leakage current mustnot exceed 1/2 mA. In case a measurement is outside ofthe limits specified, there is a possibility of shock hazard,and the receiver should be repaired and rechecked beforeit is returned to the customer.Figure 13AG-520VDH