Basically dead mobiles are called as not getting to turning on or not able to boot a mobile phone.
- Most of the dead mobile phone problems are causes with battery and its performance.Approximately battery voltage is3.7v you can check this with using multimeter in voltage mode, if it is around 3.6v you can proceed to next step or else proceed in further.
- You can boost your battery with battery booster.
- After boosting your battery check the voltage again, if it is boosted at rated voltage you can proceed to next step. Or else change the battery and proceed to next step.
Note 1: if you have service station or DC machine you can check with that also.
Note 2: you carefully watch the battery performance after boosting.Because some cases battery will drain automatically after certain time. If you are facing this issue change the battery and proceed to next step.
Check board short or not.
You can check this on battery connector (+ve,-ve) terminal, in multimeter continuity mode.