Understanding Power Button Functionality and Diagnosing Voltage Issues in Mobile Devices

When it comes to repairing mobile devices, understanding the power button functionality and diagnosing voltage issues is crucial. In this article, we'll dive into how the power button works, how to identify voltage problems, and various techniques to help you become a proficient mobile technician.

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Step 1: Understanding the Power Button Circuit

The power button is designed to be simple to use, but understanding its inner workings can help you diagnose issues more effectively. When you press the power button, the 4.3 volts present on pin number three goes to ground, signaling the device to change from a high state (4.3 volts) to a low state. In some cases, even if the correct voltage is present, the device may not turn on, indicating an issue elsewhere in the circuit.

Step 2: Identifying Voltage Issues

The V_battery voltage is present in various components, such as the bobbin and capacitors. If no voltage is detected on the battery connector, the problem may lie within the efpmic sector, a common issue in Android devices. Repairing this issue typically takes about half an hour and can cost between 60 to 150 Euros, depending on the device.

Step 3: Assessing the OVP and IF Pmic Sectors

Inspect the ovp input and output voltage to determine if there are any failures in this sector. If the voltage is detected, the issue likely lies in the efpmic sector, which is responsible for delivering current to the battery connector. If this sector is damaged, the device will experience a lack of voltage.

Step 4: Diagnosing Breakdowns Quickly

While having a thermal camera can help diagnose faults in less than five minutes, it's not necessary for successful repairs. A schematic can provide valuable information to identify the problem. If the ifpmic is heating up, the solution is to replace it with a new one, as charging circuits like Pmic and If Pmic are prone to internal damage. Other circuits, like audio, CPU, and memory, can be reflowed to resolve issues.

Step 5: Detecting Hot Spots without a Thermal Camera

A thermal camera isn't the only way to detect hot spots in electronic circuits. The rosin technique is a simple method that can help you identify overheating components. Apply rosin to various areas and observe which components heat up when connected to the laboratory power supply. You can find numerous videos on our channel and YouTube that explain this technique in detail.

Step 6: Measuring Voltages on Input and Output Capacitors

When the device is turned on, the back bobbin must have an output voltage, indicating that the pmic is functioning correctly. To diagnose issues, measure the voltages on input and output capacitors. If you don't have a schematic diagram, count the inductors near the pmic to determine the circuit's inputs and outputs. These inductors are present in all mobile motherboards. Simultaneously, count the boost line capacitors and ensure they are the same size. Measure the boost line voltage to check if the correct input voltage is present.

Step 7: Checking Capacitor Voltages

Capacitor voltages are typically the same as the battery voltage without pressing the power button. Measure the voltage of each capacitor to ensure it's at the correct value. This will help you identify any voltage issues and determine if further repairs are needed.

By following this detailed guide, you can become proficient in understanding power button functionality, diagnosing voltage issues, and repairing mobile devices. Continually refine your skills and invest in better equipment to stay ahead of the competition and offer professional, reliable repair services.

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