My LG 42CS570 will not come on, has no picture or sound. The power indicator on the front flashes twice very slow then turns blue. Any idea what may be the problem?

These blinks [flashes] are fault indication (Error Codes). From the number of blinks occur at one time switch ON, you can get an idea about the faulty circuit section inside it. This will make repair easy. These are called blinking codes. Make sure about the exact number of blinking of the standby/power LED, by switching On & OFF the set, for at least two times. Count it carefully. If you wish to get some details, check the site linked here. It has details about blinking codes, and fault locating procedure, to many popular brand TVs and other devices.
http://electro-medical.blogspot.com/
http://electronicshelponline.blogspot.com/
If blinks continue without any pause, the main board is faulty.

5 years ago he wanted help probably threw it away before now

These blinks [flashes] are fault indication (Error Codes). From the number of blinks occur at one time switch ON, you can get an idea about the faulty circuit section inside it. This will make repair easy. These are called blinking codes. Make sure about the exact number of blinking of the standby/power LED, by switching On & OFF the set, for at least two times. Count it carefully. If you wish to get some details, check the site linked here. It has details about blinking codes, and fault locating procedure, to many popular brand TVs and other devices.
http://electro-medical.blogspot.com/
If blinks continue without any pause, the main board is faulty.

Corrupted firmware. A firmware update is necessary. These blinks [flashes] are fault indication (Error Codes). From the number of blinks occur at one time switch ON, you can get an idea about the faulty circuit section inside it. This will make repair easy. These are called blinking codes. Make sure about the exact number of blinking of the standby/power LED, by switching On & OFF the set, for at least two times. Count it carefully. If you wish to get some details, check the site linked here. It has details about blinking codes, and fault locating procedure, to many popular brand TVs and other devices. http://electronicshelponline.blogspot.com/

These blinks [flashes] are fault indication (Error Codes). From the number of blinks occur at one time switch ON, you can get an idea about the faulty circuit stage inside it. This will make repair easy. These are called blinking codes. Make sure about the exact number of blinking of the standby/power led, by switching On & OFF the set, for at least two times. Count it carefully. If you wish to get some details, check the site linked here. It has details about blinking codes, and fault locating procedure, to many popular brand TVs and other devices. Viewing it in "Mosaic" will make surf easy.
http://electronicshelponline.blogspot.com/
Blinking codes details to many popular brand TVs are given. Surf the site with patience.

suspect either a back light power board issue or main power board to back light board issue...also, is it under warranty ?

Hi, Ephraim. The flashing red light indicates that the device is showing "low battery". It could be that the LG phone charger fits the charging port on your bluetooth headset but it is not compatible with your device. In order for you to know that it is charging, the device should show a steady red light(means charging).
Please take a look at the table reference below.
----------------------------------------------------------------------
•With the Charger Plugged In
______________________________________________________________________
•Headset Indicator Headset Status
Red-----------------------------------------------Charging (battery level less than 50% charge)
Yellow-------------------------------------------Charging (battery level more than 50% charge)
Green--------------------------------------------Charging complete
----------------------------------------------------------------------
======================================================================
======================================================================
======================================================================
----------------------------------------------------------------------
With No Charger Plugged In
__________________________
Headset Indicator Headset Status
______________________________________________________________________
Off ---------------------------------------------Power off
Three blue flashes------------------------Powering on/off
Steady blue --------------------------------Pairing/connect mode
Rapid blue/purple flashes -------------Connection successful
Quick blue flash --------------------------Incoming/outgoing call
Slow blue pulse --------------------------Connected (on a call)
Slow blue flash ---------------------------Standby (not on a call)
Slow red flash ----------------------------Idle (not connected to phone)
Slow purple pulse -----------------------Connected call muted
Steady red ---------------------------------Attempting to connect
Quick red flash ----------------------------Low battery

Note: After 20 minutes on a call or of inactivity, the light stops flashing to conserve power, but the headset remains on
----------------------------------------------------------------------

Hope that'll help you in some way.
**Please rate my post and/or leave a comment** ...Thanks...

Try the old flashlight test, turn off the lights in the room. Turn on the set and flash a bright flashlight on the screen. Do you see the image or is the screen totally black?? If you see the image, then most likely you have a backlight problem. Verify that you have 24V on the power supply for the inverter

Its not going to be a do it yourself repair--likely a bad board or even boards--have a repair center (authorized for this brand) inspect it.

Just getting a set like this apart safely is tricky.

Under a year old tv?This tv have power supply problems.Call the for warrenty repair.Or tries websites like shopjimmy.com,Ebay.com to buy a refurbish power supply board for the replacement.