Akash

Both 5C &5S have same battery.By seeing that there is something mistake on SWI lines.Check the center point of battery that connect properly.

That is the Audio ic issues that some pin are broken under Audio ic.

Some small mistake makes the phone near to die.There the possible of that problem is. 1- Conform that all screw are in good position most of the cases long screw over the battery . 2- If the phone LCD was insert while on on condition light coil must be burnt cause no light. 3- Remove home button flex and try. 4- iTunes detect the phone or not on DFU mode check that and post the comment.

There are a few things related that issues that can be fixed by following steps. 1.       iTunes is the source to find that problem so restore via iTunes with latest version. 2.       See Error if not happen there is two sector for repair.One is baseband and other is NFC related issues. 3.      Both cases have different symptoms if the shut down message popup means that the issues of baseband related. 4. If 3 no message not shows and not activate means that is the problem of NFC. Better put the snap that is best for solution find.

If the same issue happen after the tristar replacement that must be other fault.Check all pad below tristar and also check the SWI line and see battery data present on 3uTool or not.Yes most of the Tristar is common in iPhone.This will help to find out the compatibility of Tristar.

have you ever changed the charging flex.WI-FI and bluetooth aerial is not Network antenna any more.Possible solution. 1- Antenna is connect to charging flex. 2- Bad contact of antenna to antenna connector.

First check out phone detect on dfu mode or not via iTunes.If PC detect the phone restore it .If not try to force DFU mode.Finally if all fails that must be hardware issues.

There is many issues that you have to insert password and trust to connect.Yes PC detect the phone but you can`t enter password,So i think without solving the long screw you can`t connect to PC anymore.

Brother clearly observe the home button Fpc might be tore or home button not connect probably and ic on the home button flex damage cause that issues.Sometime display also cause that issues because display have home button flex.

iUnable to activate related to baseband issues.If the phone fails to detect IMEI while on activating the phones.There is common problem shows on.The way of repair that problem .1- BBPMU reball 2- Wtr problem 3- BBCPU reball That need to hardware skill that can`t be fixed with software.