Well, that sounds like you're screen has a loose connector, i sugest you open up the phone, search through the guides to find the guide that is conform woth you're phones model, and that you fix this loose connection, the problem can acure when the phone has been dropped on the floor or that you dropped the phone to hard on a hard surface. Open up the phone, locate the screen connector on re-connect the connection properly, i hope this may help you. Greetings
Just get a broken 6 plus from eBay or something, the 6S plus is a newer revision of what looks like the same phone, but in fact it is TOTALY different . . . Their is nothing you can use out of a 6s plus that you can use in a normal 6 plus . . .
Their is one other thing that you can try to do, if you put the imac on a table, screen facing down on a towel or something, you should open the bay where the memory goes, on the bottom left side, look inside the imac with a flashlight, you might see a lila/red colored button, thats the PMU reset button, press it when the unit is OF the power, another thing that crosses my mind and what you can try is resetting the SMC of your imac. Unplug the power, keyboard and mous, press the power button for about 5 seconds, then plug everything back in and see if the imac will boot, if it doesnt, its more likely to have a power supply/analog board faillure due to age. Good luck with your lovely imac :)
Apple wants you to throw away you're device when the battery starts to lose power over time . . . Some old apple employee even did confess that apple would build in some kind of chip that counts the age of the battery, how many times the battery has been charged and discharged, and that the battery starts to perform less when she meets the days/cycles counts, programmed in this chip, so when the laptop leaves the warrenty period, that the battery (or even some other components) would start to fail over time . . . Even other manufacturers do this kind of stuff, the machine is great when it is still in the garantee-period, but when the garantee period is over (mostly after 2 years), than the device/machine starts to show problems . . . And if you dont beleive me, its very simple, take a washing machine from the early 90's, and you will see that, even today, it will work just fine, but wait 10 years from now, and then you buy a washing machine made in this time right now, you won't get the same performance EVER ...