Denon PMA-50 Service Manual

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Contents

SAFETY PRECAUTIONSThe following items should be checked for continued protection of the customer and the service technician.leakage current checkBeforereturningthesettothecustomer,besuretocarryouteither(1)aleakagecurrentcheckor(2)alinetochassisresistance check. If the leakage current exceeds 0.5 milliamps, or if the resistance from chassis to either side of thepower cord is less than 460 kohms, the set is defective.Be sure to test for leakage current with the AC plug in both polarities, in addition, when the set's power is in each state(on,offandstandbymode),ifapplicable.CAUTION Please heed the following cautions and instructions during servicing andinspection.◎ Heed the cautions!Cautions which are delicate in particular for servicingare labeled on the cabinets, the parts and the chassis,etc. Be sure to heed these cautions and the cautionsdescribed in the handling instructions.◎ Cautions concerning electric shock!(1) AnACvoltageisimpressedonthisset,soifyoutouch internal metal parts when the set is energized,youmaygetanelectricshock.Avoidgettinganelectricshock,byusinganisolatingtransformerand wearing gloves when servicing while the set isenergized,orbyunpluggingthepowercordwhenreplacing parts, for example.(2) Therearehighvoltagepartsinside.Handlewithextra care when the set is energized.◎ Caution concerning disassembly andassembly!Through great care is taken when parts weremanufacturedfromsheetmetal,theremaybeburrsontheedgesofparts.Theburrscouldcauseinjuryiffingersare moved across them in some rare cases. Wear glovestoprotectyourhands.◎ Use only designated parts!Theset'spartshavespecificsafetyproperties(fireresistance,voltageresistance,etc.).Besuretousepartswhich have the same properties for replacement. Theburrs have the same properties. In particular, for theimportantsafetypartsthatareindicatedbythez markon schematic diagrams and parts lists, be sure to usethe designated parts.◎ Be sure to mount parts and arrange the wiresas they were originally placed!Forsafetyseasons,somepartsusetapes,tubesorotherinsulatingmaterials,andsomepartsaremountedawayfrom the surface of printed circuit boards. Care is alsotakenwiththepositionsofthewiresbyarrangingthemandusingclampstokeepthemawayfromheatingandhighvoltageparts,sobesuretoseteverythingbackasitwasoriginallyplaced.◎ Make a safety check after servicing!Check that all screws, parts and wires removed ordisconnected when servicing have been put back in theiroriginal positions, check that no serviced parts havedeteriorate the area around. Then make an insulationcheck on the external metal connectors and betweenthe blades of the power plug, and otherwise check thatsafetyisensured.(Insulationcheckprocedure)Unplug the power cord from the power outlet, disconnectthe antenna, plugs, etc., and on the power. Using a 500Vinsulation resistance tester, check that the insulationresistancevaluebetweentheinplugandtheexternallyexposedmetalparts(antennaterminal,headphonesterminal,inputterminal,etc.)is1MΩorgreater.Ifitisless, the set must be inspected and repaired.Manyoftheelectricandthestructuralpartsusedinthesethavespecialsafetyproperties.Inmostcasesthesepropertiesaredifficulttodistinguishbysight,andtheuseofreplacementpartswithhigherratings(ratedpowerandwithstandvoltage)doesnotnecessarilyguaranteethatsafetyperformancewillbepreserved.Partswithsafetypropertiesareindicatedasshownbelowonthewiring diagrams and the parts list in this service manual.Be sure to replace them with the parts which have thedesignated part number.(1) Schematicdiagrams.......Indicatedbythez mark.(2) Partslists.......Indicatedbythez mark.The use of parts other than thedesignated parts could cause electricshocks,firesorotherdangeroussituations.CAUTION Concerning importantsafety parts6