Chosen Solution
was fixing my iPhone 6 housing, battery and screen. because it was broken. and after I install it all. the logic board are getting really hot when I turn it on and the screen does not work ( I have tried the screen on another iPhone and it works fine)
If the logic board is uncomfortably hot, then there may be a short circuit somewhere. Double check your work and check the connectors and flexes for any sign of damage. If you connect the phone to iTunes enabled computer, does it get recognized? That would be an indication that the device is booting but the issue is with the display. Then check to see if the backlight is on. Bring the phone in a dim or dark room or look at the edge of the screen. If the backlight is not working, then shine a bright light on the screen to see if you have a dim image.
