Black screen Samsung tv

In most of the case, the back lights LED strips have defective LED diode on it.

I hate to give you bad news but you damaged the LCD panel when you had it out and its either live with the lines or throw the TV away, its easy to damage the panel when handling them

Please un-plug the cable between the main board & the power supply, apply the AC power to it, if the back lights come on & still on, replace the main board; if the back lights did not come on, mostly the problem is defective back light LED strips.

Normally the T-Con board will cause this loss of video image. You can order parts from any of the many TV parts suppliers online, just Google "Samsung TV repair parts" Remember this is just a guess since the diagnostics have not been run.

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.
Search the site by type in the "brand name" to your device, in the "Search box at the top right of the display window of the Homepage" to get gathered related posts.

perhaps the backlight invertor driver circuit.

Samsung TV Repair Part Number Identification Backlight Inverters LED...
See where the wires from the long LED strips on the both sides of the screen lead you to.

does your model have separate board for backlight ? or is it integrated with TCON ?

Check and replace its T'Con board.
http://electronicshelponline.blogspot.com/

With most of the modern model LED TVs from Samsung, the T'Con board is a built in part of the display panel, and is not replaceable. If you wish to get some details; check the site linked here. Pull up older posts.
http://electronicshelponline.blogspot.com/
faults & possible causes to LCD & Plasma screen are given with illustrations. You can get an idea about the fault to an extent. Faults to all LCD & Plasma screen are similar, irrespective of its brand and screen size.

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://electro-medical.blogspot.com/
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. To some models sets, the back-light inverter and SMPS section circuit will be integrated at its main board itself. If so; the main board should be replaced. To some models of sets, all these section circuit will be integrated at its main board. If this is the case, you have to replace the main board.

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. To some models sets, the back-light inverter and SMPS section circuit will be integrated at its main board itself. If so; the main board should be replaced. To some models of sets, all these section circuit will be integrated at its main board. If this is the case, you have to replace the main board.