Samsung UN55F6350AFXZA, partial backlight failure, scorched components

[gustagen]

Hi again! I've had great success with repairing several LCD monitors and TVs with the help of the friendly members here.

I recently rescued a Samsung UN55F6350AFXZA from the curb.

I powered it up and let it run for about an hour. It seemed to work fine other than half of the backlights not functioning, and a dark splotch near the upper left corner of the screen.

I disassembled it and found some scorched components on one of the backlight strips. There are also components on other strips that appear to have been overheated, with discoloration showing through the mounting tape.

The dark splotch seems to have been caused by the missing section of the reflector and soot on the diffuser. I shined a powerful flashlight through the screen while displaying an image and it appears undamaged.

Oddly, all but two of the LEDs on the scorched strip are still functioning. The third LED from the scorched area gets very hot, and I can smell the small lens melting.

Will a full set of new replacement backlight strips remedy the issue?

Is there possibly a separate root cause further back in the circuit that needs to be addressed first?

Thanks for any help you can offer!

[budm]

Re: Samsung UN55F6350AFXZA, partial backlight failure, scorched components

I would replace all the strips.
https://www.badcaps.net/forum/attach...2&d=1567020745
That looks like poor solder joints that heated up.
https://www.badcaps.net/forum/attach...1&d=1567020745
Those 3 black SMD devices look to be part of the protection circuit.
You are lucky that the panel did not catch on bigger fire and burn down the house. when you finish the repair, male sure to turn down the backlights level on all inputs to as low as possible. They drive the LED's way too hard so they fail very often.

[nomoresonys]

Re: Samsung UN55F6350AFXZA, partial backlight failure, scorched components

Backlight current mod: https://www.youtube.com/watch?v=ogtfojsIZK8

[gustagen]

Re: Samsung UN55F6350AFXZA, partial backlight failure, scorched components

Thanks budm! I think you've been involved in all of my repairs here so far.

Thanks to you, I already know about turning down the backlight level to prevent future problems.

I will look for a deal on a complete set of new replacement strips.

[gustagen]

Re: Samsung UN55F6350AFXZA, partial backlight failure, scorched components

Thanks nomoresonys! The video you linked to shows similar scorching in a different area of the backlight strips. Scary stuff!

I will probably just lower the backlight level as budm suggests, rather than make changes to the hardware as the video shows.

Thank you for the link.

[nomoresonys]

Re: Samsung UN55F6350AFXZA, partial backlight failure, scorched components

It's not for everyone, it can be a little tricky.

[gustagen]

Re: Samsung UN55F6350AFXZA, partial backlight failure, scorched components

I just ordered a full set of new strips.

I will report back when they arrive and I install them.

While I wait, I’ll stay busy attempting to patch the burn hole in the paper reflector. Any suggestions?

I plan on rotating the reflector and the diffuser panels so that any minor difference in light with be in the lower right corner of the screen rather than the upper left.

[llonen]

Re: Samsung UN55F6350AFXZA, partial backlight failure, scorched components

You know its well time a class action suit was brought against these companies

[nelson suram]

Re: Samsung UN55F6350AFXZA, partial backlight failure, scorched components

Amigo deberias de regular el voltaje de los LEDS para darle mas vida a los mismos.. utilizando una resistencia mas alta entre el source del mosfet que alimenta a los leds

[gustagen]

Re: Samsung UN55F6350AFXZA, partial backlight failure, scorched components

The replacement backlight strips arrived a couple days ago.

I managed to install them and get the TV reassembled without issue.

I patched the melted area of the backlight reflector with a small piece of thick white paper coated with gloss white spray paint. There’s no sign of the repair, even when displaying a solid light-colored background.

I turned the backlight level down to 12 out of 20.

I’ve logged about 12 hours on it with no problems.

Thanks budm and everyone else for the help!