Notes on the Troubleshooting and Repair of Television Sets

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Table of ContentsPrefaceAuthor and CopyrightDISCLAIMER

IntroductionTelevision at the crossroadsTelevision receiver fundamentalsTV repairRepair or replace

TV Receivers 101Subsystems of a television setWhy projection TVs are not just normal TVs in big boxesFor more information on TV technologyOn-line tech-tips databases

CRT BasicsColor CRTs – shadow masks and aperture grillsDegaussing (demagnetizing) a CRT

TV Placement And Preventive MaintenanceGeneral TV placement considerationsPreventive maintenanceWarning about using a TV as a computer or video game display

TV TroubleshootingSAFETYSafety guidelinesWarning about disconnecting CRT neck boardTroubleshooting tipsProgram to aid in diagnosing TV set problemsTest equipmentIncredibly Handy widgetsSafe discharging of capacitors in TVs and video monitorsAdditional information on discharging CRTsRemoving the CRT HV connectorSafe troubleshooting techniques for line powered TVsThe series light bulb trickGetting inside a TVSpecific considerations before poking around inside a TV or monitorDusting out the inside of a TVTroubleshooting a TV with the mainboard disconnected

TV AdjustmentsUser picture adjustmentInternal adjustmentsFocus adjustmentAdjustment of the internal SCREEN and color controlsOptimal procedure for setting brightness/background and screen adjustmentsColor balance adjustmentMore on Calibrating TV colorHorizontal position, size, and linearity adjustmentVertical position, size, and linearity adjustmentPincushion adjustmentsGeometry adjustmentWhy is the convergence on my set bad near the edgesCRT purity and convergence problemsCRT purity adjustmentCRT convergence adjustmentTilted pictureB/W TV size, position, and geometry adjustments

Low Voltage Power Supply ProblemsLow voltage power supply fundamentalsStandby power suppliesTypical TV power supply front endTotally dead setIntermittently dead set – bad cordsetPower button on set is flakeyTV blows fuseFuse blows or TV blows up when sync is disruptedInternal fuse blew during lightning storm (or elephant hit power pole)Fuse replaced but TV clicks with power-on but no other actionPower-on tick-tick-tick or click-click-click but no other actionNo picture or raster and no soundReduced width picture and/or hum bars in picture and/or hum in soundExcessive B+ from fixed regulator like STR30123/STR30130/STR30135TV power cycling on and offDead TV with periodic tweet-tweet, flub-flub, or low-low voltageBypassing the Startup CircuitShorted ComponentsStartup problems – nothing happens, click, or tick-tick-tick soundTV turns off after warming upTV doesnt power up immediatelyOld TV requires warmup periodTV shuts down with bright picture or when brightness is turned upRelays in the Power Circuitry of TVsWhat is a posistor?Flameproof ResistorsWidth and height change with warmupProblems with SCR based regulatorsTV shuts down with dark picture or when changing channels

Deflection ProblemsDeflection fundamentalsAbout the vertical scan ratePicture squeezed in then diedTV non-linearityHorizontal deflection shutting downTV will not syncHorizontal lock lostInsufficient width (without hum bars)Vertical lock lostVertical squashedPart of picture cut offSingle Vertical LineSingle Horizontal LineKeystone shaped pictureLoss of Horizontal Sync (also applies to vertical) after WarmupIntermittent jumping or jittering of picture or other random behaviorHorizontal output transistors keep blowing (or excessively hot)Horizontal output transistors blowing at random intervalsVertical foldoverComments on vertical problemsJagged or uneven vertical sweepExcessive width/pincushioning problemsDeflection yoke testingDeflection yoke repairTesting of flyback (LOPT) transformers

High Voltage Power Supply ProblemsHV power supply fundamentalsWhat is a tripler?High voltage shutdown due to X-ray protection circuitsLow or no high voltageExcessive high voltageSnaps, crackles, and other HV breakdownArcing, sparking, or corona from CRT HV anode (red wire/suction cup)Arcing from flyback or vicinityDaves complete procedure for repair of an arcing flybackArcing at spark gaps and gas discharge tubes on CRT neck board or elsewhereArcing due to bad connections to or disconnected CRT returnFlashovers inside the CRTOzone smell and/or smoke from TVX-ray and other EM emission from my TV or monitor?Should I be worried about X-ray exposure while servicing a TV or monitor?More on radiation from TVs and monitorsFlyback shot by 4 year old with water pistolBlooming or breathing problemsErratic focus or screen (G2) voltage and/or controls on flybackFocus/Screen divider bypass surgeryDecaying or erratic focus or screen (G2) voltagesDisconnecting flyback wire(s) from CRT driver boardFocus or screen voltage drifts after warmup only when CRT is connected

Raster, Color, and Video ProblemsNo color – black and white pictureSaturated color but almost no brightnessBrightness control has no effectOne color is too weak or too strongPsychodelic colorNo picture/dark picture/erratic pictureTV and monitor manufacturing quality and cold solder jointsWhy cant TV manufacturers learn to solder properly?Intermittent or missing colorsSome commentary on monitor and TV whackingRetrace lines in pictureWhite/gray retrace linesRed, green, or blue retrace linesBad CRT causing retrace linesRed, green, or blue full on – fog over pictureShorts in a CRTProviding isolation for a CRT H-K shortRescuing a shorted CRTPicture tube replacementHigh voltage to focus shortDark pictureBrightening an old CRTPicture tube brightenerMore drastic measures to brighten CRTLeft portion of screen is dark or fadedColor balance changes across screen from left to rightBleeding highlightsTrailing lines in one or more colorsBrightness changes from left-to-right across screenPicture fades in and outOccasional brightness flashesExcessive brightness and/or washed out pictureBad focus (fuzzy picture)Focus drift with warmupBad focus and adjustment changes brightnessCharlies comments on focus problemsBlank picture, good channel tuning and soundPurple blob – or worseColor rings – bullseye patternMagnet fix for purity problems – if duct tape works, use it!Color TV only displays one colorDisappearing Red (or other color)The wandering black blob on old SonyVertical brightness or color bars

Tuner, AGC, and Sync ProblemsNo reception from antenna or cablePicture is overloaded, washed out, or noisyJumping picture on white scenesInterference when using VCR RF connectionRF Interference on TVProblems with ground loops and video hum barsMissing or noisy channel or block of channelsLoss of Channel after WarmupChannel tuning drifts as set warms upNoise in picture and sound due to bright sceneInternal interference – switchmode power supplies and digital circuitryThose darn rabbit earsHerringbone lines in pictureEM or RFI hell?

Audio ProblemsPicture fine, no audioWeak or distorted audioBuzzing TVChattering yokeHigh pitched whine or squeal from TV with no other symptomsReducing/eliminating yoke noiseWhining when off?

Miscellaneous ProblemsGeneral erratic behaviorWiring transmitted interferenceJittering or flickering due to problems with AC powerTV blows fuses or trips breakers or worse when A/V connections are madeMy TV has the shakesTV displays black box with normal picture borderAdvertising overloadStrange codes appearing on TV screenReleasing demo modeTV was rained onTV was droppedReally cleaning a TV inside and outSetup menus will not go away or hieroglyphics on screenSetup adjustments lost – TV service codesService menu cautionStrange number in upper left corner in Magnavox service modeTV doesnt work after being in storageOlder TVs with multiple intermittent problemsTV has burning smellStatic discharge noise and picture tube qualityRevival of dead or tired remote control unitsProblems with the IR remote receiverSo you lost your original remote (or it fell in the toilet)Loudspeakers and TVsShould I replace all the electrolytic capacitors if I find a bad one?Sweet little old ladies and TVs from atticPhantom spot or blob on CRT after set is shut offComments on bright spot at power-offDisposing of dead TVs (CRTs and charged HV capacitors)Shock and/or spark when connecting cable or other A/V componentsWhat is the deal with Macrovision copy protection?AGC and copy protectionOn-screen clock runs slow or fastCold problems with cold TVs – or – an unhappy ChristmasF-connector broken off rear of TV or VCR

Some Model Specific ProblemsErratic problems with older GE TVsErratic problems on late model GE, RCA, or ProScan TVSylvania/Magnavox/Philips – no startupSony TVs/monitors and HstatMore on HstatNo video on late model Sony TVs

Items of InterestVarious video standardsAn informal history of X-ray protectionWhat is this goop around some electrolytic capacitors and other components?What does the flyback (LOPT) transformer do?Why do flyback (LOPT) transformers fail?Brief comments on testing the HOTCRT rejuvenationMemory chips in TVsHow does Picture-In-Picture (PIP) work?Tonys notes on setting convergence on delta gun CRTsSaga and general setup for large CRT TVsLiquid coupling fluid for projection TVsOrigin of burn spot/line on projection setBlue focus different for projection sets?Comments on color purity, set orientation, and domingAbout instant-on TVsAbout gadgets to use house wiring as TV antennaCan I add an S-Video input to my TV or VCR?How do I add A/V inputs or outputs to a TV which does not have them built in?Can I add direct RGB inputs to a TV?Adding variable volume headphones to a TVBuilding a Frankenstein TVTurning a TV (or monitor) into an oscilloscope?Displaying a video signal as a picture on an oscilloscopeUse of surge suppressors and line filtersComments on lightning damageGFCI tripping with TV, monitor, or other high tech equipmentMultisystem TVsPlaying NTSC videotape on a PAL TVBuying a TV in EuropeCould a TV be modified for 3D (stereo) display?Displaying TV on a computer monitorDisplaying computer video on a TVHow can I couple 4 TV screens to make them act like only one?What is Scan Velocity Modulation?About Automatic Black Level Stabilization and possible problemsWhat is Kell factor with respect to interlaced displays?Homemade V-chip (or at least viewing limiter)What is Aquadag?Combined computer monitor and TVInteresting TV Switch Mode Power SupplyThe horizontal output transistor substitution jig trickKens comments on (TV) SMPS repairIR detector circuitUK Satellite TV information

International Color Television StandardsBrief description of international color TV standardsSome questions and answers about TV standardsPolitically Correct TV StandardsVariations on a standard – the PAL systemWhat about PAL sets WITH a tint/hue control?TV, shortwave, power worldwideColor television standards worldwideCable channel allocationNotes on cable and broadcast frequenciesHow did the (vertical) frame rate get chosenWhy is the NTSC color subcarrier such a weird frequency?What is the maximal allowed deviation of the horizontal frequency?Informal comparison of TV standardsPAL-plusMore information about watching NTSC video on PAL systems

Service InformationAdvanced TV troubleshootingService manuals for really old TVsHow to locate service info when all the little stickers have fallen offTechical assistance help numbersWeb resourcesParts informationSuggested referencesFCC ID Numbers of TVsInterchangeability of componentsHorizontal output transistor pinoutsHow do you locate the HOTReplacement power transistors while testingTesting of replacement HOTsRemoving and replacing the deflection yokeSwapping of deflection yokesSwapping of CRTsDecayed glue in electronic equipmentRepair parts sources