Trying to diagnose symptoms of failing Samsung LCD TV LN46D630M3FXZA

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.

try to resolder the pins of the chroma IC and some possible lose connections you can see in the PCB board...

Kindly review the following to potentially identify the defective part
Repair Tutorial LCD TV Parts Overview Common Symptoms Solutions How...
some sites where you get parts are
TV Parts Universal TV Stands DLP Chips ShopJimmy LCD TV
Samsung TV Parts eBay
LG TV Boards Parts and Components
LCD TV Parts eBay

You have to check the back light inverter of the tv. check the videos to identify the parts
http://electro-medical.blogspot.com/


. LCD TV Repair Tutorial Backlight Inverter Common Symptoms Solutions How to...

Hi Shawn,
If your LCD TV or monitor has stopped working, or is displaying one of the following symptoms, then it's a candidate for some new capacitors
- Flickering screen
- Screen image disappears after several seconds
- Dim screen
- Slow start
- Power LED on, but no picture
- Unusual colors and/or lines
The primary cause of LCD TV and monitor failure is caused by faulty capacitors. You can examine the capacitors in your LCD TV or monitor and actually see if they are bad.
If they appear bulged on top, then they need to be replaced.
New capacitors will solve a host of problems in LCD monitors and TV's and will extend the life of your monitor or TV by several years.
Check the cables, connectors and connections.
Take it to a repair shop.
https://www.youtube.com/watch?v=TR2iWN6b-LY
LCD TV Repair No Power Power Supply Common Symptoms Solutions How to...

If your LCD TV or monitor has stopped working, or is displaying one of the following symptoms, then it's a candidate for some new capacitors
- Flickering screen
- Screen image disappears after several seconds
- Dim screen
- Slow start
- Power LED on, but no picture
- Unusual colors and/or lines
The primary cause of LCD TV and monitor failure is caused by faulty capacitors. You can examine the capacitors in your LCD TV or monitor and actually see if they are bad.
If they appear bulged on top, then they need to be replaced.
New capacitors will solve a host of problems in LCD monitors and TV's and will extend the life of your monitor or TV by several years.
Check the cables, connectors and connections.
Take it to a repair shop.
https://www.youtube.com/watch?v=TR2iWN6b-LY
LCD TV Repair No Power Power Supply Common Symptoms Solutions How to...

Hi Brenda,
If your LCD TV or monitor has stopped working, or is displaying one of the following symptoms, then it's a candidate for some new capacitors
- Flickering screen
- Screen image disappears after several seconds
- Dim screen
- Slow start
- Power LED on, but no picture
- Unusual colors and/or lines
The primary cause of LCD TV and monitor failure is caused by faulty capacitors. You can examine the capacitors in your LCD TV or monitor and actually see if they are bad.
If they appear bulged on top, then they need to be replaced.
New capacitors will solve a host of problems in LCD monitors and TV's and will extend the life of your monitor or TV by several years.
Check the cables, connectors and connections.
Take it to a repair shop.
https://www.youtube.com/watch?v=TR2iWN6b-LY
LCD TV Repair No Power Power Supply Common Symptoms Solutions How to...

This is a typical symptom of a failing LCD screen inverter board or LCD screen backlight lamp. The backlight lamp failure symptoms are very similar to the inverter board failure symptoms. If you have to guess which one is causing the problem, try replacing the inverter board first. LCD screen inverter boards fail more often than the LCD screen backlight lamps.

The black screen problem of your TV can be attributed to a backlight driver failure, busted backlight, or LCD driver failure.

The flickering indicates a failing backlight driver or a failing backlight. The screen should be totally black, without any glow, when either of them is not working. To verify, grab a torch and shine it on the screen. You will be able to see a faint display telling you that the backlight is busted or the backlight driver is faulty. If not, the LCD driver or the LCD panel itself is faulty, although it has a low probability due to the symptoms of the problem. The only way to fix the problem is replacement of the faulty part. You may need the service of a qualified technician to determine exactly which one is the root of the problem that needs replacement.