HOW TO DIAGNOSE A FAILED T'CON BOARD HOW TO REPLACE A T'CON BOARD T'Con boards Sony T'Con board
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Samsung Samsu ng T'Con board
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DIAGNOSING A FAILED FAILED T'CON BOARD All vide o inputs inputs receiv ed by the vide o process circuits are handled on a frame-by frameby-frame -frame basis. The vide o frames frames are conve rte d and scaled to 8 to 10 bit RGB information. It is is virtually impossible for the video process circuit to cause a problem on a specific area of the scree n. Failures on this board usually appear as distortions, color leve l shifts, vide o lev el shifts or noise that involv es the entire picture . The T’Con T’Con can gene rate symp sy mptom toms s that appear to be video process related, but the video process circuit cannot produce the sy symptom mptoms s of a failed T’Con T’Con board circuit. T'CON FAIL F AILURES URES Failures in the timing timing control circuits circuits of the T’Con T’Con can produce symptoms symptoms of absolutely no video or generate lines and patterns that usually cover all or a substantial substantial part of the scre en. Dete rmini rmining ng if the T’Con T’Con is the cause of a ‘No Video’ Video’ condition is a bit more difficult since since th ere are no indications on the scree n to analyze. analyze. M any of the Sony TV models ove the last few
years will dete ct a T’Con that has completely failed. The communications data between the video process circuits and the T;Con will cease to communicate, iif the T’Con fails comple te ly. This will cause the TV to shut down and display a diagnostic code , indicating a failure of the T’Con. Not all chassis designs have th is feature and it is not found on olde r models. The typical scenario whe n this failure arises is for the technician to bring a vide o process board to the re pair location. It is usually safe to assume that the problem lies on the T’Con board, if the replacement video board dos not giv e a solution to the problem since it is highly unlikely that a rep lacement board with the same failure was rece ive d. One trick to check most T’Cons for functionality is to loosen the LVDS connector at the T’Con while unit is turne d ON. Handle the LVDS connector with care and be certain to fully rele ase the lock tabs. Gently rock the cable in and out of the connector while observing the screen for any response. Depending on the chassis, the symptoms of the scre en ma be ge ntle white flashe s, intermittent coloure d lines, or a scree n full of random pattern s. The idea at this point is to provoke some kind of respon se on the scree n. Anothe r helpful pro cedure is to rapidly heat and/cool the T’Con with a hot air devices or circuit coolant and watch for patterns appear on the screen.
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LVDS cable failures Although the proble m with LVDS cable or conne ctors can gene rate symptoms of T’Con failure s this usually tend s to be intermittent and wiggling of the conne ctors will usually prov oke a change in the symptom on the scree n. LVDS cable and conne ctors have be came rathe r robust ove r the past few years. Technicians who damage the m cause most proble ms and this is gene rally quite ob livious upon close e xamination. LVDS CABLE
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LCD pane l failures Some LCD panel failures could possibly mistaken for T’Con board issues. Other t han damage to the LCD glass, most panel failure s are isolated to a particular area of the scree n. Since the T’Con disperse s the pixel data to groups of line and column dirve IC’s situated on the outer edges of the panel, it is unlikely that more than one of the se IC’s would fail at the same time. Mu ltiple columns of struck on or stuck off pixels are there fore , more likely to be the fault of the T’Con circuits. The same applie s to a single row of lit or unlit pixels. The T’Con simply cannot cut out a single line of information.
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T'CON REPLACEMENT In many instances, replacement of the T’Con board will be relative ly straight forward. In some case, the othe r boards may have to be loosene d or re moved to allow access to the mounting screws and clearance to remov e the T’Con board. The issue of most concern is keep ing track of the he at transfer pads, stand offs and insulators. The T’Con is heav ily shielded and it si ease to hav e one or more of the se components accidentally fall out of the asse mbly when re moving. T’Con assemblies that use multiple heat transfe r pads must be re move d slowly and ev er y attempt must be made to keep the shield and circuit board together as they are remov ed from the unit. Check for any serv ice bulletins pertaining to the model and panel de sign that contain the subje ct lie of ‘T’Con heat transfer pad locations’ for pictures to show the prope r location of these components. This site itself has cover ed disassembly proced ure to some model LCD TVs, here . Pull up older posts he re, or see the site in Timeslide option, which can be accesse d by the drop down at the top left side of the display window. It will make search the e asily. Remove the scre w from the LVDS cable ground strap so the cable can be move d away. Unplug the connector to inverter board and remove harness from the re tainer. Remove all screws securing the board sub-chassis to the pane l. Pull the top of the board toward you and downward to allow access to the bottom scre ws securing T’Con. The position of screws, and disassembly method may vary set to set. Carefully unpe el the conductive tape from the top bracket taking care not to tear them. Leave the tape attacked to the T’Con shield. Remove the top bracket cove ring the gate and source driver components. This will allow access to the upp er flat cable conne ctors, if any. Carefully lift the locking tabs securing the flat cables. Leave the fat cables attached to the T’Con and shield ass;y. the T’Con board will have an insulating pad betwe en it and the LCD panel that will cause the board to stick. Not much effor t is required to re lease it. The goal at this point is to remove the board and shield together so as to avoid dropping heat transfer pads and insulators located be tween the front of the board and the shield. If successful, Both components should stay toge ther as insulated. Note the spaces mounte d on the backside of the board. These will need to be transferre d to the rep lacement board. Lift the circuit board upward slowly while observ ing
the location of the he at transfer and insulating pads. In most cases the heat transfe r pad will remain attached to the ir appropriate ICs and the insulating pads will be struck to the shield. If anything falls off, use the instruction to retu rn them to their proper position. Transfer all heat and insulating pads along with the flat cables to the replacemen t board. Once the components have bee n transferre d to the front of the circuit board, attach the shield and flip the asse mbly. Transfer any spacers or insulating pads to the replacement bard. Temporarily secure the T’Con board to the shield with ele ctrical tape. This helps in prev enting move ments of the circuit bard while installing the assembly back into the LCD panel. Once the T’Con ass’y is secure d to the panel, inser t and lock the flat cables. Plug in all conne ctors and secure the board sub chassis. Do not forge t about the wire harness that was removed from its retainer.
Posted 24th June 2013 by Gopakumar Gopalan
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