How to repair dead mobile phone

How to repair dead mobile phone

1.chack battery (if remove able)
2.change battery (if remove able)
3.open the mobile phone and check with the DC power supply
4.open back plane and middle plame
5.chack on/off switch
6.clean the PCB best quality thinner
7.chack shorting
8.chack volt on/off switch (2.7-3.7)
9.change switch on/off
10.give hot air on the mother board
11.give hot air on the cpu/power ic
12.connect to the DC power supply and see on DC power supply display
13.if some ampire show on display like- (1-4,1-6,1-8,1-9 etc) and set not got on then may be software fault
14.upload software with oppropriate software flashing tools
15.move CPU/power ic
16.rebull power ic /CPU
Change power ic/CPU