Chosen Solution
Hi! After I replaced old power, volume and mute button flex cable with new one and after cleaning front camera, I turned on iPhone 5 and saw black screen without Apple logo, only black shine. I tried to resolve problem by pressing power and home button but it didn’t work. I also checked connection between screen and iPhone and it is OK (cables are OK).
Some connector inside the iphone is been inserted the wrong way. open up the iphone and check. you could have also damaged parts by shorting them or electro-static discharge.
