How To Turn On A Mac Monitor Without Power Button. Use an external mouse or trackpad and keyboard to operate the laptop. If this is working it means your computer is able to get enough power from the power source and that the power cable is also working.
Make sure the Mac is turned off. Immediately push and hold the option command P and R keys on your keyboard. Check the ports on your Mac to find out whether you need an adapter.
To give you some context.
If you turn it off you would have to open the lid again and turn the Mac on again first. If your computer is a MacBook Pro 13 Retina Display Late 2013 Model A1502 then you can either briefly shorten pin5 and pin29 on the keyboard connector or shorten out the power-pads as shown on the image. So because its normally on a table stand shelf see the screenshot getting down to the power on button is a slight. If there is no startup sound release the keys after the second time the Apple logo disappears.
