Badcaps.net Forum
Go Back   Badcaps Forums > Troubleshooting Hardware & Devices and Electronics Theory > Troubleshooting TVs and Video Sources
Register FAQ Calendar Search Today's Posts Mark Forums Read

 
Thread Tools Display Modes
Old 02-04-2021, 04:24 PM   #1
Jackching
Member
 
Join Date: May 2017
City & State: PEI
My Country: Canada
I'm a: Knowledge Seeker
Posts: 63
Default LG 50LF5800-UA Backlights flicker on and off

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?
Attached Images
File Type: jpg IMG_2021-02-04-13-52-47-999.jpg (780.2 KB, 11 views)
Jackching is offline   Reply With Quote
Old 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: 1,351
Default 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/
neilc6 is offline   Reply With Quote
Old 02-04-2021, 04:37 PM   #3
dick_barton
Badcaps Veteran
 
dick_barton's Avatar
 
Join Date: Aug 2015
City & State: Cardiff
My Country: Wales
Line Voltage: 230V AC, 50Hz
I'm a: Hobbyist Tech
Posts: 6,544
Default 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.
dick_barton is offline   Reply With Quote
Old 02-04-2021, 08:37 PM   #4
Jackching
Member
 
Join Date: May 2017
City & State: PEI
My Country: Canada
I'm a: Knowledge Seeker
Posts: 63
Default Re: LG 50LF5800-UA Backlights flicker on and off

Quote:
Originally Posted by neilc6 View Post
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?
Jackching is offline   Reply With Quote
Old 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: 1,351
Default Re: LG 50LF5800-UA Backlights flicker on and off

About $32 USD on ebay from China.
neilc6 is offline   Reply With Quote
Old 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
Default 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
handsworth is offline   Reply With Quote
Old 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
Default Re: LG 50LF5800-UA Backlights flicker on and off

What are you guys typing in to find these for this model?
Jackching is offline   Reply With Quote
Old 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: 7,711
Default 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.
nomoresonys is offline   Reply With Quote
Old 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
Default 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?
Jackching is offline   Reply With Quote
Old 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: 7,711
Default Re: LG 50LF5800-UA Backlights flicker on and off

Those should work, says direct replacement for those models in description.
nomoresonys is offline   Reply With Quote
Old 03-10-2021, 02:26 PM   #11
Jackching
Member
 
Join Date: May 2017
City & State: PEI
My Country: Canada
I'm a: Knowledge Seeker
Posts: 63
Default Re: LG 50LF5800-UA Backlights flicker on and off

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.
Attached Images
File Type: jpg IMG_20210310_161510.jpg (255.1 KB, 11 views)
File Type: jpg IMG_20210310_161518.jpg (242.5 KB, 14 views)

Last edited by Jackching; 03-10-2021 at 02:29 PM..
Jackching is offline   Reply With Quote
Old 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: 7,711
Default Re: LG 50LF5800-UA Backlights flicker on and off

You mean the plastic standoffs?
nomoresonys is offline   Reply With Quote
Old 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
Default 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..
Jackching is offline   Reply With Quote
Old 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
Default 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.
handsworth is offline   Reply With Quote
Old 03-10-2021, 05:11 PM   #15
Jackching
Member
 
Join Date: May 2017
City & State: PEI
My Country: Canada
I'm a: Knowledge Seeker
Posts: 63
Default Re: LG 50LF5800-UA Backlights flicker on and off

Quote:
Originally Posted by handsworth View Post
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
Jackching is offline   Reply With Quote
Old 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
Default 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.
handsworth is offline   Reply With Quote
Old 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
Default 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?
Jackching is offline   Reply With Quote
Old 03-12-2021, 06:31 AM   #18
dick_barton
Badcaps Veteran
 
dick_barton's Avatar
 
Join Date: Aug 2015
City & State: Cardiff
My Country: Wales
Line Voltage: 230V AC, 50Hz
I'm a: Hobbyist Tech
Posts: 6,544
Default Re: LG 50LF5800-UA Backlights flicker on and off

Could you have glued the broken standoff's. Superglue or something similar.
dick_barton is offline   Reply With Quote
Old 03-12-2021, 10:55 AM   #19
Jackching
Member
 
Join Date: May 2017
City & State: PEI
My Country: Canada
I'm a: Knowledge Seeker
Posts: 63
Default Re: LG 50LF5800-UA Backlights flicker on and off

Quote:
Originally Posted by dick_barton View Post
Could you have glued the broken standoff's. Superglue or something similar.
I could try that with hot glue or something
Jackching is offline   Reply With Quote
Old 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
Default 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..
Jackching is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump



Badcaps.net Technical Forums 2003 - 2022
Powered by vBulletin ®
Copyright ©2000 - 2022, Jelsoft Enterprises Ltd.
All times are GMT -6. The time now is 02:32 PM.
Did you find this forum helpful?