Common GSM Faults I SS1 Computer Hardware & GSM Repair Lesson Note

This lesson note focuses on the “Big Three” problems that bring customers to a repair shop. When a phone doesn’t “work,” 90% of the time, it’s one of these issues. As a technician, your job is to be a detective—finding the smallest, simplest solution first.

The Detective’s Mindset (Troubleshooting)

Before you open a phone, you must ask the customer questions. This is called Diagnosis.

• “Did it fall into water?”
• “Did it drop on a hard floor?”
• “Did it just go off while you were charging it?”

If a phone won’t turn on, we don’t just start changing the screen. We check the Power Path: Charger → Charging Port → Battery → Power Button → Motherboard.

Charging Faults (The “Mouth” Problems)

This is the most common fault in Nigeria, often caused by dust, bad cables, or rough handling.

Common Symptoms:

• The phone only charges when you “wiggle” the cable.
• The phone says “Charging” but the percentage stays at 0% (Fake Charging).
• Nothing happens at all when you plug it in.

The Fix:

1. The Dirt Check: Use a thin needle or tweezer to gently pull out lint/dirt from the port. You’ll be surprised how much “pocket dirt” gets stuck in there!
2. The Cable Test: Always try a known “good” charger before blaming the phone.
3. Port Replacement: If the internal gold pins are bent or broken, you will need to use your Hot Air Station to remove the old port and solder on a new one.

Battery Faults (The “Fuel” Problems)

Batteries have a heartbeat, and eventually, they get tired and “die.”

Common Symptoms:

• The “Quick Drop”: The phone is at 80%, then suddenly jumps to 10% in five minutes.
• The “Bulge”: The back of the phone is pushing out or the screen is lifting (this is a swollen battery).
• The “Shut Down”: The phone goes off as soon as you try to make a call or open a heavy app like TikTok.

The Fix:

• Calibration: Sometimes the “brain” of the phone just needs to be reset by charging it to 100% and letting it die to 0% once.
• Replacement: If the battery is swollen or over two years old, it must be replaced. Never try to “press” a swollen battery flat.

Power Issues (The “Dead” Phone)

When a phone is completely “dead” (won’t turn on), it’s usually a break in the electrical circuit.

Common Causes:

1. Deep Discharge: Sometimes a battery is so empty (0V) that the charger isn’t strong enough to “wake it up.” You might need to use a DC Power Supply to “kickstart” or “boost” the battery.
2. Faulty Power Button: If the tiny ribbon cable behind the button is torn, the phone is fine, but it can’t hear you telling it to “Wake up!”
3. Short Circuit: If water got inside, it might be connecting two parts that shouldn’t touch. This “shorts” the board, and the phone stays off to protect itself.

Practical Tips & Safety

As a student technician, follow these steps when a “dead” phone arrives on your table:

• Step 1: The Multi-meter Test. Set your multi-meter to DC Voltage. Touch the battery terminals. If it reads less than 3.4V, the phone won’t turn on. It needs a boost.
• Step 2: The USB Ammeter. Use a special charger that shows “Amps.” If the phone is taking 0.00A, it means electricity isn’t even entering the port.
• Step 3: Smell and Feel. Does the phone feel very hot in one spot? Does it smell like burnt plastic? This tells you exactly where the “Short Circuit” is located.

Quick Summary Table

Class Activity: Get a “dead” battery and a multi-meter. Measure the voltage. If it is below 3.0V, discuss why a normal charger might struggle to charge it.