If you ever wonder how to determine if the power on off switch line paths is working or not or being cut or open, when proceeding to repair a dead cell phone handset?
This one will help you to a more specific troubleshooting steps,
before looking for or applying a power ON OFF ways solution or modified jumper on it.
This tricks can be applied before or after doing the following steps in repair procedures,
1. the flash firmware is okay
2. the power switch is okay
3. the phone can charge up or accept and show charging indication on LCD display but won't power up
Here's a simple Tricks on how to determine faulty power ON/OFF switch line path on mobile phone's circuit.
By a way of Checking Resistance: This one can be applied if the power on/off line is directly connected to the Power Management IC terminal itself and no other components or open tests spot on the PCB's layout.
Set your multimeter tester to X10 or X 100 and connect the one probes to the power line path terminal of the power on off switch and the other one to the ground. Do this twice by reversing both probes position. If there is an indication of reading it means that line paths is okay, but without any response from the multimeter tester this means that the power on off switch line path is being cut or open. This technique is not just considering that every components needs a connection to the ground to work but definitely it won't work exactly without the ground connection.
By a way of checking voltage: This method can be applied by using a temporary voltage from DC Power Supply Regulator or even a battery itself, if the said handset is manageable to attach the battery without the pcb casing on it. Some mobile phones can be attachable when the battery pin connector is mounted and soldered on the PCB and unlike those have not.
Okay by checking voltage, just set the multimeter tester to 10volts DC, connect the negative probe to the PCB's groundings, then the other other one which is positive to the power on off line path. The voltage reading can reach up to 1 to 4 volts DC depending on which particular mobile phones models. The most important part on this, is that you should get readings to determine if the line paths is okay. Without any reading, the line path is seemingly open or cut.