ipad completely dead after touchscreen replacement…

hello there,

As a result of trying to plug in the touch/screen connector and (literally) run the keyboard-pins over the adjacent pins of port, you introduced 3.8V to the data lines, which receive 0.8-1.8V. In extreme cases (matrix) you sent 12/18V from the backlight circuits to i2c (0.8V) straight to the processor, which usually ends in the death of the device. The good news, however, is that this happens extremely rarely and you have to be incredibly unlucky to encounter such a case. This can only be confirmed by an electrical test and a current start-up assist. If this is the case, your iPad is rubbing a constant current of about 0.20A at startup. It seems to me that you connected the touch power supply to the control line and fried two inductors and a pull-up capacitor - which, due to its parameters, did not break into pieces but directed the 1.8V signal straight to the housing (classic short circuit). You need to analyze it, desolder the culprits, which will bring your iPad back to life - which I sincerely wish you. For the future, remember - never ever, perform operations on a connected battery of induction systems (in such cases, the voltages are much higher than the nominal ones - such as powering the matrix backlight). We start by disconnecting the power source and finish a work by connecting the power source. The safety rules for you and your equipment still apply.