Samsung UN48H4200AG Stripes on Screen: Main Board or Panel V-COM/Gamma IC Fault?

User question

TV SAMSUNG UN48H4200AG IMAGEM COM LISTRAS SOBRE POSTA ESSA TV NÃO TEM T.COM TEM V.COM E NÃO SEI SE É TELA OU A PLACA PRINCIPAL

Artificial Intelligence Response

Direct answer to the question

• Stripes on the Samsung UN48H4200AG can originate either in the main board (which generates and sends the LVDS stream) or in the panel assembly itself, where the T-CON/V-COM and gamma circuits are integrated.
• A quick, definitive test is to call up the TV’s internal test patterns from the service menu:
 – If test patterns are clean → main board is defective.
 – If test patterns show the same stripes → fault is in the panel/V-COM/gamma section (common failure of the BM81224MUV gamma IC or of V-COM power rails).
• Because the T-CON is bonded to the panel, panel-side faults are usually not economically repairable; main-board faults are solved by board swap or component-level repair.

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Detailed problem analysis

1. Signal path in this chassis
    • Main board → LVDS flat cable → Panel control board (integrated T-CON/V-COM/gamma) → Source/Gate drivers → LCD glass.
2. Symptomology
    • Vertical / horizontal or coloured stripes, present from power-on, often independent of input source.
    • If pressing or flexing the panel edge or the LVDS cable momentarily changes the pattern, suspect a panel-side problem.
3. Typical fault mechanisms
    a) Main board
     – Scaler or LVDS serializer IC failure.
     – Corrupted firmware or missing supply (12 V/5 V/3 .3 V).
    b) Panel / V-COM / gamma section
     – Gamma IC BM81224MUV or similar in short/open on one output (field-proven cause in this model, 2023–24 service bulletins).
     – Leaking electrolytic/MLCC capacitors on HAVDD/AVDD/VGH rails (e.g. CD10 reported at 10 µF / 35 V).
     – COF (chip-on-flex) driver or COG bond fracture—usually irreversible.

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Current information and trends

• Recent repair forums (Elektroda 2024) list multiple UN48H4200AG units restored by replacing the BM81224MUV gamma IC or by correcting V-COM at –4 V ± 200 mV.
• Samsung and other OEMs have migrated to “single-board” designs; dedicated T-CON boards are disappearing, making panel faults harder to service and shifting repairs toward board-level exchange.
• Growing use of programmable gamma ICs means mis-flash can mimic hardware failure; re-programming is feasible only with specialized SPI tools.

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Supporting explanations and details

Service-menu access (original remote):
Stand-by → Mute → 1 → 8 → 2 → Power
Menu » SVC » Test Pattern.
• Patterns generated inside the T-CON. Clean pattern proves panel path OK.
Critical voltages to check on panel board (typical):
 AVDD ≈ 15 V | HAVDD ≈ 7 – 8 V | VGH ≈ 22 – 28 V | VGL ≈ -5 – -7 V | VCOM ≈ -4 V.
Oscilloscope >20 MHz or differential probe useful for LVDS integrity (100 Ω pair).

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Ethical and legal aspects

• Set contains exposed mains areas; isolation transformer and ESD precautions required.
• Changing firmware parameters in the service menu may render the TV unusable—document values before altering.
• Disposal of a scrap LCD panel must follow local e-waste regulations.

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Practical guidelines

1. Visual/connector check – reseat and clean LVDS and side-bonded COF ribbons.
2. Run internal test patterns.
3. Measure panel rail voltages; compare with service manual tolerances (±5 %).
4. If panel fault confirmed yet rails are off spec, attempt:
    • Replace leaking capacitors, test/replace DC-DC IC (e.g. TPS65160).
    • Re-solder or replace BM81224MUV gamma IC (QFN 40 pins, hot-air 330 °C, 60 s, flux).
    • If rails correct but stripes persist, glass/driver bonding is defective → replace panel or scrap TV.
5. If main board fault:
    • Check 12 V, 5 V, 3 .3 V regulators.
    • Look for overheating BGA scaler (reflow rarely durable).
    • Preferred solution: board replacement (part BN94-07xxx).

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Possible disclaimers or additional notes

• Panel repair success rate for COF/gamma defects is well below 30 %; proceed only if you have QFN rework capability.
• Main board part numbers differ by region; verify suffix to retain tuner standard.
• After any gamma/V-COM work, recalibrate VCOM in the service menu to remove faint flicker.

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Suggestions for further research

• Review Samsung training guide “V-COM Adjust & Gamma Compensation 2019+ panels”.
• Study AN-1620 (TI) for DC-DC converter failure modes in LCD panels.
• Explore open-source LVDS tester projects for bench-testing detached panels.

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Brief summary

Isolate the defect with the service-menu test patterns.
• Patterns OK → replace/repair the main board.
• Patterns bad → problem inside the panel’s integrated T-CON/V-COM; most cases involve faulty gamma IC BM81224MUV or unstable V-COM rails. Limited component-level repair is possible but often not cost-effective; complete panel replacement or new TV may be the practical outcome.

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