iphone 7 not turning on repair

We recently received an iphone 7 that would not turn on.
We plugged it in to charge and got no response from the phone. We then cleaned out the charging port which made no difference.
We then cracked it open and connected up to our DC power supply, it turned on and seemed to work perfectly other than charging. We tested with a new battery and charging port which made no difference. We then tested what voltage we get through the battery connector when charging and we got a very low reading of 0.45v.
In the iphone 7 the common causes for not charging are the tristar (charging ic) and tigris (USB ic). Unfortunately on the iphone 7 when one of these IC’s goes bad it usually damages the other, this means when replacing one we will replace both for peace of mind, otherwise you may find your device suffering from the same fault in the near future.
We believe that if your going to do a job you should do it right, this is why we do repairs our own tried and tested way and if we can find a way to improve a repair, we will do so.
So we disassembled this iphone 7 and tested the charging circuit. Of Course we found low voltages on the 1v8 and 3v lines coming out of the tristar. We replaced both IC’s and this brought the voltages up to where they should be. We then cleaned the board and reassembled for testing. The phone now pulls around 1A through the charger which is perfect and is charging nicely. We are also getting 3.72v through the battery connector which is a very good reading.
The phone was then returned to the customer who was very happy to get their device back and working within a day.
If your having issues with an iphone not turning on or charging please feel free to get in touch.