What does flashing red light mean on lg 42lg50

Have you checked the outlet to see if it has power?? If not, check the circuit breaker for the outlet. Otherwise make sure all the connections on the P/S board are correct and that they are all connected.

most likely there is a bulged capacitor on the power supply, just have to replace it.

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, 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.

tv has sand but pic

Power supply module will be the first thing the Tech will look at first, parts: http://www.shopjimmy.com/catalogsearch/result/?q=LG+42LG50+

If you are going to DIY and have proper tools and know safety precaution then please read on:

Please see my basic troubleshooting guide here:
http://www.fixya.com/support/r5093881-lcd_flat_panel_tv_troubleshooting_guide

http://s807.photobucket.com/home/budm/allalbums

http://en.wikipedia.org/wiki/Capacitor_plague

An electrical pulse from the thunderstorm has affected your TV. (Was it on a surge protector?)

There is a small possibility that it will come back.

Unplug the television and let it sit for an hour or more and then re-plug it.

If you need to get a new TV, also get a good surge protector such as Panamax.

I think your mean “your TV can't turn on, and the LED red light off too” If it is true, you shall check the power switch first, because only the LG TV have the power switch (Sony 2010 model’s does). If I guess wrong, please provide more information, I wish I can help you.

If the TV is new I would suggest exchanging it..

1. Press tv on your Sky remote control.

2. Press and hold down select and the red button together until the red light at the top of your Sky remote control flashes twice.

Then enter the remote control code using the number keypad. The red light will flash twice if a valid code has been entered.

Code: 0206

4. Point your Sky remote control at your TV and press the vol + & vol - buttons. If this turns the volume up and down as you'd expect, then the tv should be set, press Select and the remote should work

try and unplug it, wait, plug back in and try it.