LG 50LF5800-UA Backlights flicker on and off

Jackching · 02-04-2021, 04:24 PM

So i ran tests on the power supply and all of the voltages going to the main board are fine. I tested all of the capacitors on the psu with an esr reader and they all pass. All diodes pass also. But when a reading is done on the 4 pin white led connector on the top of the board, the voltages will flicker to 5Vdc for a fraction of a second and go out again. For that fraction, the LED backlights light up. Anyone have any clues to this situation?

**neilc6** · 02-04-2021, 04:36 PM

Quick flash of backlights or flashing backlights are both symptoms of bad backlights. Especially on LN, LB or LF series.

https://techhometravel.com/lg-ln-ser...ed-backlights/

**dick_barton** · 02-04-2021, 04:37 PM

If your leds flicker then you must have a high voltage at the connector in order to light them up. The voltage may sharply spike at switch on and then drop quite rapidly.
Recheck the voltages at each pin to chassis at switch on and repeat for all four pins.
Quite can't see what is given on the circuit board but it looks like one set of leds run at 113V and the second set at 170V

Jackching · 02-04-2021, 08:37 PM

Quote:

Originally Posted by neilc6

Quick flash of backlights or flashing backlights are both symptoms of bad backlights. Especially on LN, LB or LF series.

https://techhometravel.com/lg-ln-ser...ed-backlights/

Unfortunately i think you are correct. I think this tv may go to the sidewalk or are there cheap led string replacements for the 50LF on aliexpress?

**neilc6** · 02-04-2021, 08:58 PM

About $32 USD on ebay from China.

**handsworth** · 02-04-2021, 09:35 PM

About $32 also on Ebay. Purchase from any one of the guys from Tucker, Ga. They get them from China and stock them in the US. About 4 days delivery time

Jackching · 02-05-2021, 02:09 AM

What are you guys typing in to find these for this model?

**nomoresonys** · 02-05-2021, 04:53 PM

There, notice the two for 32 dollars are from the U.S., look at compatible models in their description: https://www.ebay.com/sch/i.html?_fro...acat=0&_sop=15

Jackching · 02-08-2021, 06:08 AM

Would this be the right one for 50LF5800: https://www.aliexpress.com/item/4000...63504c50BkNUaT

Nine LEDs per row with five rows?

**nomoresonys** · 02-08-2021, 07:28 AM

Those should work, says direct replacement for those models in description.

Jackching · 03-10-2021, 02:26 PM

Ok so these LEDs worked fine but i ended up breaking about half of the clips off that keeps the white panel from touching the leds. Anyone know what these are called so i can order new ones? I can see the round shape of the led covers on the screen when watching tv.

**nomoresonys** · 03-10-2021, 02:31 PM

You mean the plastic standoffs?

Jackching · 03-10-2021, 02:38 PM

Whatever is in the picture there. They're called standoffs are they? Go to 7:40 in this video: https://www.youtube.com/watch?v=s4wNc3hF4JI

**handsworth** · 03-10-2021, 04:07 PM

I remove mine from the back of the panel. Push down on skinny part of tab and slide back.

Jackching · 03-10-2021, 05:11 PM

Quote:

Originally Posted by handsworth

I remove mine from the back of the panel. Push down on skinny part of tab and slide back.

Ya well it's too late for that. Half of them are broke now. Looking for a place to purchase them

**handsworth** · 03-10-2021, 05:38 PM

I got lots of extras but dont know how to ship to Canada or what it would cost.

Jackching · 03-11-2021, 05:07 PM

I can see the leds through the screen in a few places when watching tv. Im assuming its because of the few broken standoffs right?

**dick_barton** · 03-12-2021, 06:31 AM

Could you have glued the broken standoff's. Superglue or something similar.

Jackching · 03-12-2021, 10:55 AM

Quote:

Originally Posted by dick_barton

Could you have glued the broken standoff's. Superglue or something similar.

I could try that with hot glue or something

Jackching · 03-12-2021, 02:53 PM

So anyway i put all the broken standoffs back on with glue but can still see two leds shining through the screen when it's on. It's like they are brighter then the rest or something. They are especially visible when there is a lot of white on the screen in those areas. I cant figure it out. I got them from aliexpress. Maybe they're faulty. Is it possible to put the light filters back in upside down?

02-04-2021, 04:36 PM	#2
neilc6 Badcaps Veteran Join Date: Nov 2015 City & State: BC My Country: Canada I'm a: Knowledge Seeker Posts: 1,379	Re: LG 50LF5800-UA Backlights flicker on and off Quick flash of backlights or flashing backlights are both symptoms of bad backlights. Especially on LN, LB or LF series. https://techhometravel.com/lg-ln-ser...ed-backlights/

02-04-2021, 04:37 PM	#3
dick_barton Badcaps Veteran Join Date: Aug 2015 City & State: Cardiff My Country: Wales Line Voltage: 230V AC, 50Hz I'm a: Hobbyist Tech Posts: 6,544	Re: LG 50LF5800-UA Backlights flicker on and off If your leds flicker then you must have a high voltage at the connector in order to light them up. The voltage may sharply spike at switch on and then drop quite rapidly. Recheck the voltages at each pin to chassis at switch on and repeat for all four pins. Quite can't see what is given on the circuit board but it looks like one set of leds run at 113V and the second set at 170V __________________ Willing to help but I'm no expert.

02-04-2021, 08:58 PM	#5
neilc6 Badcaps Veteran Join Date: Nov 2015 City & State: BC My Country: Canada I'm a: Knowledge Seeker Posts: 1,379	Re: LG 50LF5800-UA Backlights flicker on and off About $32 USD on ebay from China.

02-04-2021, 09:35 PM	#6
handsworth Senior Member Join Date: Oct 2015 City & State: Cleveland, Ohio My Country: United States I'm a: Knowledge Seeker Posts: 119	Re: LG 50LF5800-UA Backlights flicker on and off About $32 also on Ebay. Purchase from any one of the guys from Tucker, Ga. They get them from China and stock them in the US. About 4 days delivery time

02-05-2021, 02:09 AM	#7
Jackching Member Join Date: May 2017 City & State: PEI My Country: Canada I'm a: Knowledge Seeker Posts: 63	Re: LG 50LF5800-UA Backlights flicker on and off What are you guys typing in to find these for this model?

02-05-2021, 04:53 PM	#8
nomoresonys Badcaps Veteran Join Date: Jan 2013 City & State: midwest My Country: U.S. I'm a: Knowledge Seeker Posts: 8,187	Re: LG 50LF5800-UA Backlights flicker on and off There, notice the two for 32 dollars are from the U.S., look at compatible models in their description: https://www.ebay.com/sch/i.html?_fro...acat=0&_sop=15 __________________ (Signature) One of the first and least expensive things you can do when you have an issue is take the powerboard out of the tv, flip it over and look the solder joints over with a magnifying glass if needed, add a little flux to make the solder flow well and add solder to any joints that look even a little suspect. You can practice on a scrap pcb board if needed, careful not to bridge any joints, and always let the board sit for quite a while or discharge the big caps with an appropriate resister before working on it (safety first) to try to keep from getting shocked, it doesn't take 1000 volts to KILL, a lot less can kill, so be careful, it's only a tv. THANKS FOR THE NO TIP POLICY....WELL NO TIP NO WORK.

02-08-2021, 06:08 AM	#9
Jackching Member Join Date: May 2017 City & State: PEI My Country: Canada I'm a: Knowledge Seeker Posts: 63	Re: LG 50LF5800-UA Backlights flicker on and off Would this be the right one for 50LF5800: https://www.aliexpress.com/item/4000...63504c50BkNUaT Nine LEDs per row with five rows?

02-08-2021, 07:28 AM	#10
nomoresonys Badcaps Veteran Join Date: Jan 2013 City & State: midwest My Country: U.S. I'm a: Knowledge Seeker Posts: 8,187	Re: LG 50LF5800-UA Backlights flicker on and off Those should work, says direct replacement for those models in description.

03-10-2021, 02:31 PM	#12
nomoresonys Badcaps Veteran Join Date: Jan 2013 City & State: midwest My Country: U.S. I'm a: Knowledge Seeker Posts: 8,187	Re: LG 50LF5800-UA Backlights flicker on and off You mean the plastic standoffs?

03-10-2021, 02:38 PM	#13
Jackching Member Join Date: May 2017 City & State: PEI My Country: Canada I'm a: Knowledge Seeker Posts: 63	Re: LG 50LF5800-UA Backlights flicker on and off Whatever is in the picture there. They're called standoffs are they? Go to 7:40 in this video: https://www.youtube.com/watch?v=s4wNc3hF4JI Last edited by Jackching; 03-10-2021 at 03:02 PM..

03-10-2021, 04:07 PM	#14
handsworth Senior Member Join Date: Oct 2015 City & State: Cleveland, Ohio My Country: United States I'm a: Knowledge Seeker Posts: 119	Re: LG 50LF5800-UA Backlights flicker on and off I remove mine from the back of the panel. Push down on skinny part of tab and slide back.

03-10-2021, 05:38 PM	#16
handsworth Senior Member Join Date: Oct 2015 City & State: Cleveland, Ohio My Country: United States I'm a: Knowledge Seeker Posts: 119	Re: LG 50LF5800-UA Backlights flicker on and off I got lots of extras but dont know how to ship to Canada or what it would cost.

03-11-2021, 05:07 PM	#17
Jackching Member Join Date: May 2017 City & State: PEI My Country: Canada I'm a: Knowledge Seeker Posts: 63	Re: LG 50LF5800-UA Backlights flicker on and off I can see the leds through the screen in a few places when watching tv. Im assuming its because of the few broken standoffs right?

03-12-2021, 06:31 AM	#18
dick_barton Badcaps Veteran Join Date: Aug 2015 City & State: Cardiff My Country: Wales Line Voltage: 230V AC, 50Hz I'm a: Hobbyist Tech Posts: 6,544	Re: LG 50LF5800-UA Backlights flicker on and off Could you have glued the broken standoff's. Superglue or something similar.

03-12-2021, 02:53 PM	#20
Jackching Member Join Date: May 2017 City & State: PEI My Country: Canada I'm a: Knowledge Seeker Posts: 63	Re: LG 50LF5800-UA Backlights flicker on and off So anyway i put all the broken standoffs back on with glue but can still see two leds shining through the screen when it's on. It's like they are brighter then the rest or something. They are especially visible when there is a lot of white on the screen in those areas. I cant figure it out. I got them from aliexpress. Maybe they're faulty. Is it possible to put the light filters back in upside down? Last edited by Jackching; 03-12-2021 at 02:58 PM..

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