I'd ask you to try what Dan said. Use a bootable drive with El capitan os and get to disk utility. See if you can get to your hard drive. If it's not repairable then format it. If you're unable format try another hard drive and install osx. I have had a number of Macbooks with similar issues. Ps if it's booting half way then your sata cable should be fine but hard drive damaged. Hope this helps.
The first thing you’ll want to do resolve nearly every power related issue on a Mac is to reset the SMC, or System Management Controller. This will dump and reset settings for anything power management related, and is long known to resolve problems with things like fans, heat, sleeping problems, and of course, display issues. If this fails then try resetting PMU disconnect the computer from the power cord, and from all other cables. Hold down the power button for several seconds to turn off the computer and let it sit for 5 min and then restart the laptop while holding down the Shift key. This restarts the computer in Safe Mode, hopefully with the screen visible again. After logging in (in Safe Mode) to make sure everything is ok. simply restart the computer the normal way, and the screen will behave normally again. Good luck