Panasonic CT27C8G - 27" COLOR TV User manual

1. Safetyprecautions
General guidelines
Anisolation transformershouldalways beusedduring theservicing ofareceiverwhose chassis
isnotisolatedfrom ACpowerline. Use atransformerofadequatepowerrating as thisprotects
thetechnicianfrom accidentsresulting inpersonal injuryfrom electrical shocks. Itwill also
protectthereceiverfrom being damagedbyaccidental shorting thatmay occur during servicing.
Whenservicing, observe theoriginal leaddress, especiallyinthehigh voltagecircuit. Replace all
damagedparts(alsopartsthatshowsignsofoverheating.)
Always replace protective devices, suchas fishpaper, isolation resistorsand capacitors, and
shieldsafterservicing thereceiver. Use onlymanufacturer’srecommendedrating for fuses,
circuitsbreakers, etc.
High potentialsarepresentwhenthisreceiverisoperating. Operation ofthereceiverwithoutthe
rearcoverintroduces dangerfor electrical shock. Servicing shouldnotbeperformedbyanyone
who isnotthoroughlyfamiliarwiththenecessaryprecautionswhenservicing high voltage
equipment.
Extremecareshouldbepracticedwhenhandling thepicturetube. Rough handling may cause it
toimplodeduetoatmosphericpressure. (14.7lbspersq. in.). Donotnick or scratchtheglass or
subjectittoanyunduepressure. Whenhandling, usesafetygoggles and heavy gloves for
protection. Dischargethepicturetubebyshorting theanodetochassisground (nottothe
cabinetor toothermounting hardware). Whendischarging connectcoldground (i.e. dagground
lead)totheanodewithawellinsulatedwireor use agrounding probe.Avoidprolongedexposure
atclose rangetounshieldedareas ofthepicturetubetopreventexposuretoxray radiation.
Thetestpicturetubeusedfor servicing thechassisatthebenchshouldincorporatesafetyglass
and magneticshielding. Thesafetyglass provideshielding for thetubeviewing area againstx
ray radiation as well as implosion. Themagneticshieldlimitsthexray radiation around thebell of
thepicturetubeinaddition totherestricting magneticeffects. Whenusing apicturetubetestjig
for service, ensurethatthejigiscapableofhandling 50kV withoutcausing xray radiation.
Beforereturning aservicedreceivertotheowner, theservice technicianmustthoroughlytest
theunittoensurethatiscompletelysafetooperate. Donotuse alineisolation transformerwhen
testing.
Leakagecurrentcoldcheck
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Unplug theA.C. cord and connectajumperbetweenthetwoplug prongs.Measuretheresistance
betweenthejumperedACplug and expose metallicpartssuchas screwheads, antenna
terminals, control shafts, etc. Iftheexposedmetallicparthas areturnpathtothechassis, the
reading shouldbebetween240k and 5.2M . Iftheexposedmetallicpartdoes nothave a
return pathtothechassis, thereading shouldbeinfinite.
Leakagecurrenthotcheck
Plug theACcord directlyintotheACoutlet. Donotuse anisolation transformerduring thecheck.
Connecta1.5k 10 watt resistor inparallel witha0.15 Fcapacitor betweenanexposed
metallicpartand ground. Use earthground, for exampleawaterpipe.
Using aDVMwitha1000 ohms/voltsensitivityor higher, measuretheACpotential across the
resistor.
Repeattheprocedureand measurethevoltagepresentwithall otherexposedmetallicparts.
Verifythatanypotential does notexceed0.75 voltRMS. Aleakagecurrenttester(sucha
Simpson model 229, Sencoremodel PR57 or equivalent) may beusedintheabove procedure, in
whichcase anycurrentmeasuremustnotexceed0.5milliamp. Ifanymeasurementisoutofthe
specifiedlimits, thereisapossibilityofashock hazard and thereceivermustberepairedand
recheckedbeforeitisreturnedtothecustomer.
Hotcheck circuit
Insulation test
Connectaninsulation testerbetweenanexposedmetallicpartand A.C. line. Apply1080VAC/
60Hzfor 1second. Confirm thatthecurrentmeasurementis0.5mA~2.0mA. Repeattestwith
othermetallicexposedparts.
X ray radiation
WARNING
Thepotential source ofxray radiation intheTV setisinthehigh voltagesection and thepicture
tube.
NOTE
Itisimportanttouse anaccurate, calibratedhigh voltagemeter.
Setthebrightness, picture, sharpness and color controlstominimum.
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Measurethehigh voltage. Thehigh voltageshouldbe29.25 ±1.25kV. Iftheupperlimitisoutof
tolerance, immediateservice and correction isrequiredtoinsuresafeoperation and toprevent
thepossibilityofprematurecomponentfailure.
Horizontal oscillator disablecircuittest
Thistestmustbeperformedas afinal check beforethereceiverisreturnedtothecustomer. See
horizontal oscillator disablecircuitprocedurecheck inthismanual.
2. Service notes
NOTE
These componentsareaffixedwithglue. Becareful nottobreak or damageanyfoil underthe
componentor atthepinsoftheICswhenremoving. Usuallyapplying heattothecomponentfor a
shorttimewhiletwisting withtweezerswill break thecomponentloose.
Leadless chipcomponent(surface mount)
Chipcomponentsmustbereplacedwithidentical chipsduetocritical foil track spacing. There
areno holes intheboard tomountstandard transistorsor diodes. Somechipscapacitor or
resistor board solderpadsmay have holes through theboard,howevertheholediameterlimits
standard resistor replacementto1/8watt. Standard capacitor may alsobelimitedfor thesame
reason. Itisrecommendedthatidentical componentsbeused.
Chipresistor have athree digitnumerical resistance code, 1stand 2nd significantdigitsand a
multiplier. Example:162 =1600 or 1.6k resistor, 0=0 (jumper).
Chipcapacitorsgenerallydo nothave thevalueindicatedon thecapacitor. Thecolor ofthe
componentindicates thegeneral rangeofthecapacitance.
Chiptransistorsareidentifiedbyatwolettercode. Thefirstletterindicates thetypeand the
second letter, thegradeoftransistor.
Chipdiodes have atwoletteridentification codeas perthecodechartand areadual diodepack
witheithercommon anodeor common cathode. Check thepartslistfor correctdiodenumber.
Componentremoval
1. Use solderwick toremovesolderfromcomponentend capsor
terminal.
2. Withoutpulling up, carefullytwist thecomponentwithtweezersto
break theadhesive.
3. Donotreuse removedleadless orchipcomponents since theyare
subject tostress fractureduring removal.
Chipcomponentinstallation
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1. Putasmall amountofsolderon theboardsoldering pads.
2. Holdthechipcomponentagainst thesoldering padswithtweezers
orwithaminiaturealligatorclipand applyheat tothepadarea
witha30 watt iron until solderflows. Donotapplyheat formore
than3seconds.
Howtoreplace flatic(requiredtools)
1. Removethesolderfromall ofthepinsofaFlat ICbyusing a
desolderbraid
2. Puttheiron wireunderthepinsoftheFlat ICand pull itinthe
direction indicatedwhileheating thepinsusing asoldering iron. A
small awl canbeusedinsteadoftheiron wire.
3. Removethesolderfromall thepadsoftheFlat ICbyusing ade
solderbraid
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4. Position thenew Flat ICinplace (applythepinsoftheFlat ICto
thesoldering padswherethepinsneedtobesoldered). Properly
determinethepositionsofthesoldering padsand pinsby
correctlyaligning thepolaritysymbol
5. Solderall pinstothesoldering padsusing afinetippedsoldering
iron
6. Check withamagnifierforsolderbridgebetweenthepinsorfor
dryjointbetweenpinsand soldering pads. To removeasolder
bridge, use adesolderbraidas showninthefigurebelow
IMPORTANT
Toprotectagainstpossibledamagetothesolidstatedevices duetoarching or staticdischarge,
make certainthatall ground wires and CRTDAGwirearesecurelyconnected.
CAUTION
Thepowersupplycircuitisaboveearthground and thechassis
cannotbepolarized. Use anisolation transformerwhenservicing
thereceivertoavoiddamagetothetest equipmentortothe
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chassis. Connect thetest equipmenttotheproperground(hot) or
(cold)whenservicing, orincorrect voltages will bemeasured.
2.1. X-RayProtection CircuitCheck&Adjustments
Thistestmustbeperformedas final check beforethereceiverisreturnedtothecustomer. If
voltages areoutoftolerance, immediateservice and correction isrequiredtoinsuresafe
operation and topreventthepossibilityofprematurecomponentfailure.
Equipment:
1. Isolation transformer.
2. High voltagemeter.
3. D.C. Ammeter
4. Shortjumper.
5. HHSjig(See figurebelow).
DiodeConnection Jumper.
Preparation:
1. Make surethereceiveristurnedoff.
2. Connect thereceivertoanisolation transformer.
3. Connect theammeterserial fromtheflyback anodeleadtothe
picturetubeanodesocket.
4. Prepareshortjumperand HHSjig.
Procedure:
1. Connect theshortjumperbetweenTPD16 &TPD17.
2. Connect thejumperdiodebetweenTPD14 and TPD15 (anode
connectedtoTPD15 and cathodetoTPD14).
3. Apply75VACtoACinputofisolation transformer.
4. Turnthereceiveron.
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5. Applyamonoscopepattern.
6. Set customerpictureand brightness controlstotheminimum.
7. Set currentwithin50 Ato100 Abychanging thepictureand
brightcontrols.
8. Slowlyincrease ACvoltageat theinputoftheisolation
transformerand confirm HHSvoltagemeasure33kV.
9. Turnpoweroff and removejigs.
3. EEPROMreplacement
IfanewEEPROMintegratedcircuitisreplacedfor servicing, followthenextprocedureonce that
thememoryisproperlyassembled:
1. Entertoservice mode.
2. TurntheTVset ON.
3. Once insideservice modethefirst imagethat appearson-screen
istheID1registerwiththerespectiveaddress value(FF)like the
imagebelow.
Note:
All 3registers(ID1,ID2,ID3) shouldappearwithFF values ifanew
EEPROMisassembled.
4. With“VOL”keysadjust thecorrect valueaccording withthe
service adjustmenttable(see “Service Mode”section on page15).
5. Changetothenext IDswitchregisterwith“CH”keysand repeat
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thesameprocedureas step4.
6. Whenreplacing anew EEPROMbesuretoset thecorrect ID
switchvalues foreachmodel.
7. Once that all 3registersareset withthecorrect address value,
perform all oftheremaining adjustments and servicing.
IMPORTANT:
Correct IDswitchconfiguration shouldbeinputwhenreplacing
EEPROMforeachtelevision model, otherwise ifwrong values are
configured, thetelevision softwarewill notfunction accordinglyand
properly.
4. About lead free solder(PbF)
NOTE
Leadislistedas (Pb)intheperiodictableofelements. / Intheinformation below, Pbwill referto
leadsolder, and PbF will refertoLeadFree Solder. / Theleadfree solderusedinour
manufacturing process and discussedbelowis(Sn+Ag+Cu). / ThatisTin(Sn), Silver(Ag)and
Copper(Cu)although othertypes areavailable.
Thismodel uses PbFree solderinit’smanufactureduetoenvironmental conservation issues. For
/ service and repairwork, we’dsuggesttheuse ofPbfree solderas well, although Pbsoldermay
be/ used. / PCBsmanufacturedusing leadfree solderwill have the“PbF”or aleafsymbol
stampedon the/ back ofPCB.
CAUTION
-Pbfree solderhas ahighermelting pointthanstandardsolder.
Typicallythemelting pointis50 ~70 °F(30 ~40 °C)higher. Please
use ahigh temperaturesoldering iron and set itto700 ±20 °F(370
±10 °C).
-Pbfree solderwill tend tosplashwhenheatedtoo high (about1100
°For600 °C). / Ifyou must use Pbsolder, please completely
removeall ofthePbfree solderon thepinsorsolderarea before
applying Pbsolder. Ifthisisnotpractical, besuretoheat thePb
free solderuntil itmelts, beforeapplying Pbsolder.
-Afterapplying PbF soldertodoublelayeredboards, please check
thecomponentsideforexcess solderwhichmayflow ontothe
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opposite side.
SuggestedPbfree solder
Thereareseveral kindsofPbfree solderavailablefor purchase. Thisproductuses Sn+Ag+Cu
(tin, silver, copper)solder. However, Sn+Cu(tin, copper), Sn+Zn+Bi (tin, zinc, bismuth)soldercan
alsobeused.
5. Receiverfeaturetable
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