How to use Digital Multimeter in mobile phone repairing to trace fault Tutorial4

How to Use Digital Multimeter in Mobile Phone Repairing | Complete Guide for Beginners 🔧 Welcome to another informative video for mobile phone repair learners and technicians! In this video, we will learn how to use a digital multimeter for mobile phone repairing, from basic to advanced level. A multimeter is the most essential diagnostic tool in mobile phone and electronics repair – just like a stethoscope is to a doctor. Whether you're a beginner technician, a student of mobile repairing, or an experienced professional looking to sharpen your testing skills – this video is for you! ________________________________________ 📌 What You Will Learn in This Video: ✅ What is a Digital Multimeter ✅ Why a multimeter is so important in phone repairing ✅ How to test mobile phone battery voltage ✅ How to test charging voltage ✅ How to use Continuity Mode (Beep Mode) ✅ How to use Diode Mode ✅ How to use Resistance Mode ✅ Real-time mobile PCB testing examples ✅ How to trace broken tracks using a multimeter ✅ Common testing mistakes by beginners ✅ Tips and tricks for safe and accurate usage ________________________________________ 🧰 Understanding the Digital Multimeter A digital multimeter is a device used to measure different electrical values such as: • DC Voltage (used to check battery and charging lines) • Continuity (to test connections and shorts) • Resistance (to test resistors and PCB components) • Diode Mode (to check diode health and internal voltages) • AC Voltage, Temperature, Capacitance (not commonly used in phone repair) ________________________________________ 📋 Step-by-Step Guide to Multimeter Usage in Mobile Repair ________________________________________ 🔹 Step 1: Checking Battery Voltage 🟢 Whenever a dead phone comes into your workshop, the first step is to check the battery voltage. Set your multimeter to DC voltage mode (usually marked as "V⎓"). • Place the red probe on the battery positive terminal and the black on the negative. • If the voltage is above 3.7V, the battery is fine. • If it’s below 3.7V, you may need to pre-charge it or boost it before powering on the phone. ________________________________________ 🔹 Step 2: Testing Charging Path 📲 If the phone is not charging, follow this step-by-step voltage testing procedure: 1. First, check voltage at the charging port. 2. Then check voltage on the sub PCB. 3. After that, check voltage at mainboard charging IC input. 4. Step-by-step, trace the voltage path to find where power is lost. ✅ This method helps you isolate the faulty component in the charging line. ________________________________________ 🔹 Step 3: Using Continuity Mode (Beep Mode) 🔌 Continuity mode is used to check if two points are connected or not. You’ll hear a beep sound if the circuit is complete. • Use this mode to trace tracks from the sub PCB to the main PCB. • Useful to check if a track is broken or still connected. • You can also detect short circuits using continuity mode – if two points beep unexpectedly, they may be shorted. 💡 Pro Tip: Always disconnect the battery before using continuity mode to avoid damage to the multimeter. ________________________________________ 🔹 Step 4: Using Diode Mode 📉 Diode mode is also important to measure voltage drop across components and test internal lines of ICs. • Set the multimeter to diode mode (⏚ or triangle + line symbol). • Use it to check charging IC input/output, PMIC lines, VBAT, VPH_PWR, etc. • A healthy line should show a voltage between 0.3V to 0.7V in diode mode. 📍If it shows 0.000 or short beep, the line is shorted. 📍If it shows OL (Over Limit), the line may be broken. ________________________________________ 🔹 Step 5: Resistance Mode 📏 Set the multimeter to ohms (Ω) mode to check the value of resistors. • You can use it to test SMT resistors on the PCB. • It’s also used for comparing the value of components across a working and non-working board. • Helps in identifying faulty resistors or open lines. ________________________________________ 🎓 Beginner Tips for Using a Multimeter in Mobile Repair: • Always set the correct mode before testing (Voltage, Continuity, Resistance) • Use sharp probe tips for better contact with tiny components • Never test continuity while the phone is powered on • Clean the testing points on PCB if probes are not making proper contact • Practice on dead boards before testing on customer devices ________________________________________ 📚 Other Multimeter Functions (Less Common in Mobile Repair) 🔹 AC Voltage Mode – Used for household current, not required in phone repair 🔹 Capacitance Mode – Used for testing capacitors, rarely used in mobile PCBs 🔹 Temperature Mode – Only if you're using a thermocouple sensor, not essential 🔹 Frequency Mode – Not used in basic mobile repair