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[Solved] LG 55LB650V - Flashing TV Screen Issue, Capacitors Intact, Blinking 2x/sec - Help Needed

seralion 58254 16
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  • #1 17020724
    seralion
    Level 2  
    Hello. My tv blinks right after turning it on. About 2x a second. The electrolytic capacitors are all whole, or at least you can not see the defect. Please help.
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  • #2 17020893
    elcomandante
    Level 12  
    looks like a power supply problem - short circuit / overload on the output, or the power supply itself. These can be capacitors (most likely at the output of the power supply). Do you have a diagram?
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  • #3 17020986
    buli1
    Level 25  
    It's flashing, but what ?? Image? backlight? all the time flashing? is something else going on too little info ...
  • #4 17021511
    seralion
    Level 2  
    I do not have a scheme. The backlight flashes all the time round. Nothing else happens. The image itself reacts as needed. All options work. I do not know what else I could say.
  • #5 17021658
    buli1
    Level 25  
    I bet on a damaged LED backlight.
  • #6 17021857
    tomek5333
    Level 13  
    a typical symptom of backlighting, the more often in LG the ledes, rozemy matryce and check or immediately saw which diodes do not shine. With hot aire you can change the diodes themselves without having to leave any stripes
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  • #7 17021931
    niewolno2
    Level 40  
    As for the visual check of the capacitors, this is far too little and you would have to check them with a meter.
  • #8 17022814
    elcomandante
    Level 12  
    with such symptoms I would rather put on a power supply for the led-y, and it is the capacitors that are first to be replaced.
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  • #9 17118632
    ganitu
    Level 25  
    Hello, I have the same model LG and the same fault, as the repair of the above-mentioned TV ended - I put on diodes in the backlight.
  • #10 17120013
    tomek5333
    Level 13  
    remove the dies and replace the diodes as you do not have a hotair, then replace the strips
  • #11 17121256
    buli1
    Level 25  
    elcomandante wrote:
    with such symptoms I would rather put on a power supply for the led-y, and it is the capacitors that are first to be replaced.


    Buddy, you're writing nonsense .....
  • #12 17122005
    Freddy
    Level 43  
    buli1 wrote:
    Buddy, you're writing nonsense .....
    Please, justify it.
  • #13 17125222
    ganitu
    Level 25  
    In my TV there were 2 LEDs 6V 2W defective in the backlight, after the TV exchange works properly, the demolition of the matrix at such a diagonal is an extreme sport, you can sweat a little. greetings
  • #14 17125658
    buli1
    Level 25  
    Freddy wrote:
    Please, justify it.


    Buddy with all due respect, but it does not make sense to justify it. Who even had to deal with tv lg .... knows where to start, probably you know what is damaged.
  • #15 17520062
    shrederr
    Level 9  
    Damaged LEDs, standard. Greetings.
  • #16 18642435
    kusalek
    Level 10  
    Hello
    I confirm: in this case the diodes also turned out (the upper set - 3 rows, powered from a higher voltage, the left converter at the very top, looking at the power supply board from the side of the 230V socket, where there are two 33uF / 350V capacitors connected in parallel) .
    Question to Tomek5333: what idea to remove strips from sheet metal - the adhesive holds very tightly.
    Maybe other colleagues would have something to say to my last question.
    Thank you for any ideas.
    Regards
  • #17 18654802
    kusalek
    Level 10  
    And it happened.
    All lighting replaced. Original LG. 10 slats, double-sided tapes included. TV dedicated. The next day, the information that the image again lights up and disappears.
    I took again to the workshop. After switching on, it flashes. I stripped to "naked". I turned on and ..... lights up. It is true that in the first move on the slats there is a voltage of 178 and 118 V, but after a while it stabilizes on the values of 157 and 104 V. And it shines on itself.
    Anyone have any idea what might be causing the flashing? (after repair).
    I checked the electrolytic capacitors for capacity, although in the system, but the capacities were tolerant.
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Topic summary

✨ The discussion revolves around the LG 55LB650V television experiencing a flashing screen issue, with symptoms of blinking at a rate of 2 times per second immediately after power-on. Initial assessments suggest potential problems with the power supply or LED backlight. Users recommend checking for damaged LEDs, particularly in the backlight, as this is a common issue with LG models. Some responses emphasize the need for thorough testing of capacitors beyond visual inspection, while others share personal experiences of similar faults and successful repairs involving LED replacements. The conversation highlights the importance of diagnosing the backlight system and power supply components to resolve the flashing issue effectively.
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FAQ

TL;DR: LG 55LB650V flashing is usually a backlight issue; one confirmed fix replaced 2 LEDs (6V/2W). "Disassembly at this size is an extreme sport." Follow the steps below. [Elektroda, ganitu, post #17125222]

Why it matters: This FAQ helps DIYers and technicians diagnose a flashing 55LB650V fast, prioritize the right parts, and avoid panel damage.

Quick Facts

Why is my LG 55LB650V screen flashing every half-second?

That flash indicates the LED backlight protection cycling due to a fault. Members identify it as “a typical symptom of backlighting.” The LED strings open under load, the driver retries, and you see a repeating blink. Plan to inspect or replace the affected LEDs or strips. [Elektroda, tomek5333, post #17021857]

How can I tell if it’s the backlight and not the mainboard or T‑Con?

If menus and video still react while brightness pulses, the panel and mainboard are alive. That pattern points at the backlight subsystem. A user reported normal image behavior with only the backlight flashing. Check backlight connectors and strips instead of signal boards. [Elektroda, seralion, post #17021511]

Can power‑supply capacitors cause this flashing?

Yes, a short or overload on the LED output, or failing output capacitors, can cause cycling. One member flagged the supply and its output caps as suspects. Measure LED‑driver rails under load and verify capacitor ESR, not just appearance. If ripple is heavy, service the supply side. [Elektroda, elcomandante, post #17020893]

What’s the better fix: replace all strips or only the bad LEDs?

If you have hot‑air tools and skills, replace only failed diodes on the strip. If you lack hot air, replace entire strips for reliability. Full strip replacement reduces repeat openings on large panels. Keep thermal balance consistent across the set. [Elektroda, tomek5333, post #17120013]

How do I replace the backlight safely?

Do this methodically to avoid panel damage.
  1. Remove the panel and diffusers to expose strips; note strip order and wiring.
  2. Test each LED/strip; with hot air, lift and replace faulty diodes, or swap strips.
  3. Reassemble carefully, ensuring all connectors are seated and no dust remains.
“With hot air you can change the diodes themselves.” [Elektroda, tomek5333, post #17021857]

How many strips are in the 55LB650V and what voltages should I expect?

Expect 10 backlight slats in this chassis. One repair logged initial readings near 178V and 118V on two strings. They stabilized around 157V and 104V after start. Use these as sanity checks during diagnosis. [Elektroda, kusalek, post #18654802]

What tools do I need for this job?

A hot‑air rework station is the key tool for swapping individual LEDs. If you do not have hot air, plan on replacing whole strips instead. Prepare a clean, organized workspace and protect the panel throughout. Label connectors during disassembly. [Elektroda, tomek5333, post #17120013]

How do I remove LED strips that are glued tightly to the chassis?

The strips adhere very firmly to the metal sheet, so work slowly and evenly. Expect strong resistance from the adhesive, especially near the ends. Avoid twisting; lift along the length to prevent bending. Plan extra time for removal. [Elektroda, kusalek, post #18642435]

I replaced all 10 strips and it still flashes — what next?

Verify both LED‑driver outputs start high and then stabilize, as documented by another repair. Reseat backlight connectors and check for pinched cables. Confirm the replacement strips match original type and wiring. Flashing can persist until rails settle under load. [Elektroda, kusalek, post #18654802]

Is backlight failure common on this LG model?

Yes. Experienced members describe it as typical for this chassis. “Damaged LEDs, standard.” Prioritize checking the backlight before suspecting logic boards. [Elektroda, shrederr, post #17520062]

Can I trust visual capacitor checks to rule out PSU issues?

No. A good‑looking electrolytic can still be bad. “Visual check is far too little”; measure capacitance or ESR with a meter. Test in‑circuit only if supported by your instrument, or lift a lead for accuracy. [Elektroda, niewolno2, post #17021931]

What LED rating does this set use on the strips?

One confirmed case used 6V, 2W LEDs on the backlight strips. Two such LEDs failed and replacement restored operation. Use matching ratings when swapping devices or entire strips. [Elektroda, ganitu, post #17125222]

My set blinks about 2 times per second — what does that indicate?

That rate matches a documented case right after power‑on. It aligns with the LED driver retrying due to a backlight fault. Start with backlight strip and LED checks. [Elektroda, seralion, post #17020724]
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