Intelligent Sensor I have a LG LED LCD TV, Model 26LV2500, The picture is too dark. This just started happening.

Sounds like a backlight problem to me. If you input a signal to the HDMI or Composite input and then it goes black have you tried taking a flashlight to the screen to see if the picture is still there but just dark? That would indicate a backlight issue. That model appears to be an LED edge lit backlight, so if the picture is still there after going black your going to have to trace out the backlight circuit and see whats going on. Usually with LED backlighting if it comes on at all then the LED's are good, its just the driver supply thats failing to keep them on. Some TV's have a small separate board that provides the backlight control, but i suspect with this model its on the power supply board and not the motherboard. Have you checked that board? It could be bad caps on the power supply board, check the voltages to the backlighting when it lights up and then when it goes dark. It could just be some failed capacitors on the power supply causing that voltage rail to drop off.

Here is a link to the manual and other information, look it up. Product Support

the picture board has gone faulty
thee are two system boards in the set --one for sound and one for picture
if you have the number from the board you want to replace try e-bay --circuit boards for your tv and see what comes up

The most likely problem is the Backlight Inverter. It supplies the power to the LED array which illuminates the screen. If you are brave and also technically able, it can be replaced at home. Here is a video to help. LCD TV Repair Tutorial How to Replace the Backlight Inverter Board in LG...

picture board

Here is a page from the manual:
Page 72 166 LG 47LV5500

You may download the owner's manual and user guide from http://www.lg.com/us/support-product/lg-22LS3500

Have the cable company (should be able to be done over the phone) check and boot the box (reset it) and some can have this done by unplugging box and letting it self boot.

More likely the box than the set.

Such as a DVD recorder?
Yes, conventionally a recorder takes the feed from aerial or box befiore the TV but recording whatever you're watching can also be done mostly by using one of the Scart sockets usually on the back of a TV usually identified as Scart 1 AV in/out which should be connected to Scart In on a recorder.
If there are digital output sockets - and digital input sockets on a recorder - you'll get higher image and sound quality than you'll get from Scart.

Your TV has a light sensor that changes the brightness of the TV based on room brightness.

It's called an "Intelligent Sensor"

You can turn this off in your "Picture" settings.

Congrats on such a nice TV purchase.

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