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Nie, dziękuję Przekieruj mnie tamTV SAMSUNG UN40F5500AG O LADO ESQUERDO DO DISPLAY ESTA FAZENDO CONTATO COM A CARCAÇA MESMO SEM O CABO FLET T.COM DISPLAY DESCONECTADO
• If the left edge of the LCD panel is already conducting (or physically touching) the TV’s metal chassis with the T-CON flat-cable removed, the fault is almost certainly inside the panel assembly itself or in the small driver/COF (Chip-on-Flex) circuits bonded to that edge—not on the main boards.
• The contact is usually produced by one of three things: (1) loss or displacement of the insulating tape/foam that isolates the driver flex from the frame, (2) mechanical deformation of the panel or bezel that forces the driver flex against the chassis, or (3) an internal short in the driver ICs/COF that now ties panel reference (VCOM, VGL, VGH, etc.) to ground.
• Immediate action: disconnect AC, open the rear cover, perform a careful visual and continuity inspection of the left edge; if insulation can be restored with Kapton/PET tape and re-seating, do so. If the flex or the glass is cracked or the short is internal, the panel is considered irreparable in field conditions and must be replaced.
Signal isolation test you already performed
– By unplugging the LVDS/T-CON harness you removed all drive voltages to the panel. Persistent continuity to the chassis therefore localises the fault to the panel’s own electronics or its mechanical interface.
Anatomy of the UN40F5500AG panel
– The LTF400HM03 (or LSF400HM series) panel used in this model has gate/source driver COFs laminated on the top and/or sides. Each COF carries 0.3 mm-pitch copper traces and a driver IC encapsulated in epoxy.
– Samsung secures these COFs with black PET tape and a foamed spacer that keeps them ~0.4 mm clear of the aluminium bezel. Loss of that spacer creates a direct path between exposed pads on the COF and the grounded bezel.
Typical failure scenarios
a) Mechanical stress or drop: panel slides a few millimetres, COF edge touches bezel.
b) Over-tightened or missing mounting screws: uneven clamping warps the frame.
c) Aged tape: adhesive dries out, tape curls, live COF pads exposed.
d) Liquid ingress: electrolytic residues create a conductive bridge.
e) COF crack: high-voltage gate line (±15 V) arcs to the frame, visible as burn mark.
Effects you may see when the cable is reconnected
– Panel half-shutdown, vertical coloured lines, backlight protection trip, PSU over-current, or immediate power-off after relay click. Damage can propagate to the T-CON if not corrected.
Electrical confirmation
– With the set fully unplugged and caps discharged, use a DMM on continuity:
• Probe between panel frame (or any exposed COF pad) and chassis ground.
• ≤1 Ω confirms a hard short, higher but finite Ω indicates resistive or contamination path.
– Also probe VGL/VGH pads on the T-CON side (if labelled) to rule out board-level short.
• Modern mid-size LCD TVs (2018-2024) moved many power/logic functions onto “HV-COF” drivers on the glass; once these are damaged, field repair is rarely economical.
• Independent repair shops increasingly stock pre-cut polyimide tapes and 3-D printed spacers to restore insulation in borderline cases—success rate ~60 % if the COF itself is healthy.
• Panel replacement prices for a 40 in Samsung FHD are often 70-90 % of a new TV, so repairs focus on mechanical re-work first.
• Manufacturers are shifting to plastic bezels or over-moulded frames on mini-LED and QD-OLED sets to reduce metal-contact shorts.
• Driver line voltages: VCOM ≈ 6–15 V, VGL ≈ –6 V, VGH ≈ +26 V. Any of these shorted to chassis will shut down the power board via the T-CON’s power-good line.
• Kapton (polyimide) tape is preferred (dielectric strength ≈ 7 kV/mm, temperature 260 °C). Ordinary PVC electrical tape creeps and contaminates the optical stack under heat.
• Analogy: think of the COF as a “flex PCB with exposed bus bars.” If a bus bar touches the car body (bezel), it is equivalent to shorting a battery terminal to chassis in automotive wiring.
• Opening the set voids the Samsung warranty and in many jurisdictions transfers liability to the repairer for electrical safety.
• ESD precautions are mandatory—panel driver ICs have 200 V IEC-61000-4-2 sensitivity.
• Dispose of cracked LCD glass according to local e-waste and mercury backlight (if CCFL) regulations.
Step-by-step field procedure
Possible challenges
• COF already heat-damaged → panel scrap.
• Bezel warpage too large → need frame substitution or panel swap.
• Reassembly dust contamination → light spots (mura).
• If the continuity test still shows a short after insulation repair, the defect is internal—replacement only.
• The UN40F5500AG is 2013-series; spare panels are scarce. Consider a used donor set with intact panel.
• Study Samsung service manual “UN40F5500A Chassis U54A” section 4-2 (Panel Troubleshooting).
• Review IPC-A-610 section 11.2.3 for flexible circuit insulation criteria.
• Explore COF rebonding techniques (e.g., ACF bonding) if you have access to pulse heating equipment, though cost seldom justifies it for 40 in sets.
The left-edge short you observe with the T-CON cable removed indicates a panel-side fault—most often lost insulation or mechanical shift of the COF against the metal frame. Isolate power, open the set, inspect and restore insulation with polyimide tape and spacers; if the COF or glass is cracked, the only robust cure is panel replacement. Proceed with ESD and safety precautions or delegate to a professional service centre if specialised tools are unavailable.
