I think the remote is broken ,you need replace a new one.
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Https://www.Abctay.com is an tv parts online shop ,
We sell television and electrical accessories,all kinds of TV parts include power supply board, logic board, TV LED screen,
TV LCD screen, mobile phone screen, as well as various types of electronic tools,tv parts power supply,LCD,ccfl ,
LED,OLED,lcd panels,HMI,Inverter,LCD screen,lg screen,display screen,lcd monitor,lg lcd, lg monitor ,flat screen ,
touch screen,hmi,bulb,samsung, innolux ,Mitsubishi,philips, hitachi,auo,innolux,Planar, toshiba, siemens,chi mei,Weinview,
Infineon,industrial LCD,industrial control, sharp monitor,vigor plc,delta, mitsubishi lcd,omron plc,etc

screen out of works.
Abctay.com Wholesale tv parts,include TV power supply board, logic board, TV LED screen,
TV LCD screen, mobile phone screen, as well as various types of electronic tools,tv parts power supply,LCD,ccfl ,
LED,OLED,lcd panels,HMI,Inverter,LCD screen,lg screen,display screen,lcd monitor,lg lcd, lg monitor ,flat screen ,
touch screen,hmi,bulb,samsung, innolux ,Mitsubishi,philips, hitachi,auo,innolux,Planar, toshiba, siemens,chi mei,Weinview,
Infineon,industrial LCD,industrial control, sharp monitor,vigor plc,delta, mitsubishi lcd,omron plc,etc.

Abctay.com Wholesale tv parts,include TV power supply board, logic board, TV LED screen,
TV LCD screen, mobile phone screen, as well as various types of electronic tools,tv parts power supply,LCD,ccfl ,
LED,OLED,lcd panels,HMI,Inverter,LCD screen,lg screen,display screen,lcd monitor,lg lcd, lg monitor ,flat screen ,
touch screen,hmi,bulb,samsung, innolux ,Mitsubishi,philips, hitachi,auo,innolux,Planar, toshiba, siemens,chi mei,Weinview,
Infineon,industrial LCD,industrial control, sharp monitor,vigor plc,delta, mitsubishi lcd,omron plc,etc.

Hello, either the power supply is failing to power up the LED's or the LED strips in the screen have failed, a common issue with these sets. Power supply part # is EAY62169701. LED strips are only available as a complete screen assembly from LG....thanks

Fault at its main digital board. Short circuited component/s at it. Contact any service technician; or the authorized service center. If you wish to get some details; check the site linked here. Pull up older posts. http://electronicshelponline.blogspot.com/ In most cases, the main board might have to be replaced. If so, a software [firmware] update too might be necessary.

LG 42LS5700 - LG.com

www.lg.com > Home > Support > Product Support

LG ElectronicsTV/Audio/Video; TVs; 42LS5700 ... TV Support Landing Page - HDTV/Netcast/webOS 1.0/webOS 2.0 ... Adjusting Picture Settings - webOS 2.0 Video ... quality and convenience of complimentary shipping when buying directly from LG.com. ... Curved TVs · 22 Inch to 29 Inch Class TVs · 32 Inch to 39 Inch Class TVs · 40 Inch ...

Amazon.com: Customer Reviews: LG 42LS5700 42-Inch ...

www.amazon.com/LG-42LS5700-42-Inch.../B006ZH...

Amazon.com, Inc.LG 42LS5700 42-Inch 1080p 120Hz LED-LCD HDTV with Smart TV (2012 Model). byLG. Size: 42-Inch ..... images are nice and crisp when viewing HD content.

Widescreen TV Black Screen - Repair LCD LED PLASMA ...

? 3:41
https://www.youtube.com/watch?v=RbZncfiOXQA
Jul 13, 2011 - Uploaded by FixItUrselfDummy
Fix your tv with black screen blinking light, popping sound noise. ... Watch QueueQueue ... TV Black Screen - Repair LCD LED PLASMA - Problems SONY LG .... I have a 60 inch samsung DPL tv how can I stop the humming or ... What do I do if my tvturns on but its just a black screen so sound no picture?.

Sounds like a bad bulb.

https://www.Abctay.com is an online shop ,
We sell television and electrical accessories,all kinds of TV power supply board, logic board, TV LED screen,
TV LCD screen, mobile phone screen, as well as various types of electronic tools,tv parts power supply,LCD,ccfl ,
LED,OLED,lcd panels,HMI,Inverter,LCD screen,lg screen,display screen,lcd monitor,lg lcd, lg monitor ,flat screen ,
touch screen,hmi,bulb,samsung, innolux ,Mitsubishi,philips, hitachi,auo,innolux,Planar, toshiba, siemens,chi mei,Weinview,
Infineon,industrial LCD,industrial control, sharp monitor,vigor plc,delta, mitsubishi lcd,omron plc,etc.