LG 42LN5400 led issue

[Troopy]

Hi all,

Was wondering whether someone could help diagnose a problem with what looks like 2 led's on this tv

If the backlight is set around 50% at the bottom centre 1 or 2 led's struggle to light up on/off.
if i set 25% they dont light up at all and the display looks a bit grey at the 6 o'clock position.
However if i set 100% backlight the leds light but this is too bright for me.
Is this an led problem or a power issue like maybe faulty cap/board?

Thanks

[sordids999]

Re: LG 42LN5400 led issue

Posting pictures of the back of your tv showing the boards with clear pictures may help you more with fixing your problem

[Blake7]

Re: LG 42LN5400 led issue

Hi, took some images the best i could don't have a decent camera

[Diah]

Re: LG 42LN5400 led issue

If the backlight is set around 50% at the bottom centre 1 or 2 led's struggle to light up on/off.

interesting fault, from the point quoted you have 3 or more LEDs Open. other could do this if the dimming IC you will find it at the bottom of PWB had bad soldering or some SMT parts related .. would be nice if you post photo of the bottom of PWB and tell IC No.

[ReeceyBurger123]

Re: LG 42LN5400 led issue

You possibly have a shorted Led in the screen causing the others to be dim after it due to it dropping alot of current across it. Take the screen apart and see if an Led does not light up if so replace it. Also it wont be open as if it was there would be no Bl

[Malachi]

Re: LG 42LN5400 led issue

I have a set of working LEDs to this tv but may be too far to be worth while. Lol

[Diah]

Re: LG 42LN5400 led issue

LED Backlight at this post are 3.3V, on LED build of one LED light and one Z-Diode in reserve way to forward current. OPEN, mean it will not light on because the contact between Z-Diode and LED light Brocken.

short mean Z-Diode shorted but the Light Diode will still light. in this case current will rise up which will set the protection of PWD shutdown the Backlight. if protection failed then fire will see on there

he still have BL dear friend ReeceyBurger123... LOL

[ReeceyBurger123]

Re: LG 42LN5400 led issue

Diah think your wrong there, Open you get no bl at all and short you will as technically the circuit can still be completed the controller wont even really notice it