Samsung QE65S90C: Vertical Lines on Screen - Diagnosis

⚠️ SAFETY WARNING / ELECTRICAL AND MECHANICAL RISK. This television is powered by 230V and has internal capacitors on the power board that can retain dangerous residual charges even after disconnection. Furthermore, the 65-inch QD-OLED panel is extremely thin and fragile: any bending or incorrect pressure during disassembly can irreparably crack it, destroying the device. It is strongly recommended to entrust the intervention to a qualified technician to avoid electrocution or permanent damage to the TV. ReeFix provides this diagnosis for informational purposes only.

NECESSARY TOOLS

For diagnosis and potential intervention, a qualified technician may need:

• Professional Digital Multimeter: To measure voltages on control boards. Professional Digital Multimeter on eBay
• Dry Electrical Contact Cleaner: To thoroughly clean FFC/LVDS connectors.
• Replacement Flat Cables (FFC/LVDS): Specific for the Samsung QE65S90C model. Samsung QE65S90C Flat Cables on eBay
• Main Board: To be replaced if the defect lies in the video processor or the integrated T-CON section. Samsung QE65S90C Main Board on eBay

PHASE 1: Preliminary Diagnosis (User/Technician)

This phase helps to understand if the problem lies within the television or if it is caused by an external device.

1. Integrated Picture Test: Access the settings menu of the Samsung QE65S90C and start the self-diagnosis picture test.
   • If vertical lines remain visible: The fault is internal to the television. Proceed to PHASE 2.
   • If the lines disappear during the test: The problem is caused by an external source (decoder, console, PC) or a faulty HDMI cable. Try replacing the cable or connecting another device. In this scenario, the television does not require repair.

PHASE 2: Internal Technical Analysis (Qualified Technician Only)

This phase requires opening the chassis and advanced technical skills.

Cause 1: Delamination or damage to the panel's Chip-on-Film (COF) (65% probability)

• Key signs: Very thin vertical lines (often 1 or 2 pixels), which may vary in intensity when light pressure is applied to the bottom bezel or when the television reaches operating temperature.
• Why: COF chips are soldered using conductive adhesive (ACF) directly onto the OLED panel glass. Thermal stress or physical strain can cause these micro-connections to detach, interrupting the signal sent to the pixel columns. This is a typical defect in large panels.
• Verification: Visual inspection under a microscope of the ACF connections along the bottom edge of the panel to identify any signs of oxidation or detachment. Thermal monitoring of COF chips.
• Cost/Repairability: COF repair requires industrial precision machinery (bonding machine). In standard service centers, this defect leads to the replacement of the entire OLED panel, an intervention whose costs are almost always higher than the market value of a new TV.

Cause 2: Oxidation or poor contact of FFC flat cables (20% probability)

• Key signs: Unstable vertical lines, image flickering or colored bands that appear and disappear when gently moving the internal connection cables. The problem may manifest after transport or an impact.
• Why: Flexible cables connect the Main Board to the panel distribution boards. An imperfect insertion, accumulation of oxide on the pins, or micro-damage interrupts the correct flow of video data.
• Verification: Disconnection of flat cables, thorough cleaning of contacts with a specific dry cleaner, and subsequent reinsertion. Visual inspection of pins with a magnifying glass.
• Cost/Repairability: Low. Cleaning or replacing flat cables is a quick and economical operation for a specialized technician.

Often, when Samsung TV flat cables start to oxidize or make poor contact, vertical lines that change color or flicker are noticed when moving the chassis. In these cases, before assuming the worst, a thorough cleaning of the FFC connectors with a dry electrical contact cleaner can definitively resolve the defect without having to replace expensive components.

Cause 3: Fault in video processing circuits / T-CON integrated on the Main Board (10% probability)

• Key signs: Wide, geometric, symmetrical vertical lines or complex patterns covering precise portions of the screen (e.g., an exact half). The lines remain stable and are not affected by temperature variations.
• Why: The T-CON (Timing Controller) section, integrated directly on the Main Board in models of this generation, manages the synchronization of video signals for the panel drivers. A fault in this area prevents the correct display of image columns.
• Verification: Measurement of main logic voltages (VGH, VGL, VDD, VCORE) on the Main Board test points and analysis of transmission signals with an oscilloscope.
• Cost/Repairability: Medium. Requires complete replacement of the Main Board, a replaceable part whose cost varies depending on availability.

Cause 4: Minor causes (e.g., micro-cracks in the panel or power supply anomalies) (5% probability)

• Key signs: Vertical lines accompanied by dark spots on the display, sudden drops in brightness, or dead pixels.
• Why: Invisible micro-cracks on the panel glass or unstable voltages from the power supply unit (PSU) can destabilize row and column drivers.
• Verification: Visual examination of the turned-off panel with grazing light and checking the output voltages from the PSU board.
• Cost/Repairability: Variable. If the panel is physically damaged, the scenario of Cause 1 applies (uneconomical replacement). If the problem lies in the PSU, repairing or replacing the board is feasible at affordable costs.

FINAL VERIFICATION

1. If the lines persist during the integrated picture test (PHASE 1): The problem is confirmed at the internal hardware level.
2. If the fault lies in the panel/COF (65% probability): Replacing the OLED panel is almost always uneconomical compared to buying a new television.
   • Decision: Replace the device.
3. If the problem is caused by oxidation or defects in the flat cables (20% probability): The cost of restoring or replacing the cables is low.
   • Decision: Contact a technician for repair.
4. If the fault is located on the Main Board (10% probability): Replacing the main board is a feasible intervention.
   • Decision: Contact a technician to evaluate the cost-effectiveness of the repair through a detailed quote.