How to do flash light test on Toshiba model 50l1350u?

How on earth do you crack a screen!!

https://www.google.com/search?q=toshiba+modle+50l1350u+replacement+screen

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You must rescan the tv. Go into the setup mode on the remote and let it go through the complete scan with the cable or antenna is connected.

mine had x6 swollen capisitors ,i replaced all 6..got off ebay,,and it works fine now,check them all first

It's either mainboard or powerboard problem. Are you technical literate to fix it yourself? If no then bring it to repair shop. However it can be not cheap.

Could be a bad power board or the LED's in the panel are bad...test the voltages on the power board that go to the lamps and see if its ok

In most of the case, the problem is defective back lights LED strips.

Check and replace damaged component/s at its back-light inverter board, or replace this board as card basis. If you wish to get some details; check the site linked here. Surf the site with patience. Pull up older posts. It will be best to replace the inverter board as card basis.
http://electronicshelponline.blogspot.com/
To some model sets; especially LED back-lighted types; the back-light inverter circuit will be part of the main power supply board [SMPS]. In such cases, the power supply board might need replacement.

Back - light problem. Check and replace damaged component/s at its back-light inverter board, or replace this board as card basis. If you wish to get some details; check the site linked here. Surf the site with patience. Pull up older posts. It will be best to replace the inverter board as card basis.
http://electronicshelponline.blogspot.com/
To some model sets; especially LED back-lighted types; the back-light inverter circuit will be part of the main power supply board [SMPS]. In such cases, the power supply board might need replacement.

Back - light problem. Check and replace damaged component/s at its back-light inverter board, or replace this board as card basis. If you wish to get some details; check the site linked here. Surf the site with patience. Pull up older posts. It will be best to replace the inverter board as card basis.
http://electronicshelponline.blogspot.com/
In some models of LCD TVS; the backlight inverter and its T'Con board will be a part of the panel itself, and will be a built-in type inside the LCD panel. If so, they can't be replaced. In this case; a panel replacement is the only repair. For some other models, the backlight inverter section circuit will be a part of the main power supply regulator [SMPS]. To such sets, the power supply section circuit too should be troubles hooted. Contact any service technician. The circuit will differ with models and versions.
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