Hi
1 :First of all, open your phone a clean it good with alcohol, this fault is often due to liquid damage in the phone. Then reasemble and power on and see if the fault have gone away.
2 : Otherwise, get your hands on a service manual and check the following 2 components have the correct feed voltage
a: c600 ~ 3.2 v
b: c482 ~ 3.8 v
Get service manuals here.
http://eh.student.utwente.nl/~7Elandy/service_manuals/
Regards