GSM Faults and Causes – JSS2 Computer Hardware & GSM Repair Lesson Note (Second Term)

A GSM fault is a problem that stops a mobile phone from working properly.

• Everyday comparison: a person can have a headache or stomach ache, and a phone can have its own “illnesses”.
• First step in repair: find out why the phone is misbehaving before trying to fix it.
• Areas covered: network, charging, display and sound faults.

Behavioural objectives

By the end of the lesson, students should be able to:

1. Define a fault in a mobile phone.
2. Name the signs of network, charging and display faults.
3. State the causes of each fault.
4. Say what to check first for each fault area.
5. List ways of preventing phone faults.

What is a GSM fault?

A fault is any problem in a phone’s hardware or software that stops it working as it should.

• GSM: Global System for Mobile communications, the standard used by most mobile phones for calls and texts.
• Sign (symptom): what you see or hear when the phone has a problem.
• Cause: the reason the sign appears.
• Troubleshooting: checking the simple causes first, then the harder ones.

What are the types of GSM faults?

There are four common types of GSM faults: network, charging, display and sound faults.

• Network faults: the phone cannot find a signal to call or text.
• Charging faults: the battery does not charge properly.
• Display faults: the screen is damaged or shows the wrong picture.
• Sound faults: the phone gives no sound or a poor sound.

What are network faults?

A network fault is a problem that stops you calling or texting even though a SIM card is inside the phone.

What are the signs of a network fault?

• No service: the screen shows “No Service” or “Emergency Calls Only”.
• Broken voice: your voice breaks or crackles during a call.
• Weak signal: the signal bars are always low.

What are the causes of a network fault?

1. Software settings: Airplane Mode is on by mistake, or the network is set to 3G in an area that only has 4G.
2. Damaged SIM card: a scratched or dirty gold part means the phone cannot read the SIM.
3. Antenna problems: a fall can shift or break the internal antenna.
4. Network IC fault: the small chip on the circuit board that handles the signal has failed, so the phone never finds a signal.

What are charging faults?

A charging fault is a problem that stops the battery percentage from rising when the phone is plugged in.

• Note: this is one of the most common complaints brought to phone repairers.

What are the signs of a charging fault?

• Wiggling: you must wiggle the cable before charging starts.
• False charging: the phone says “Charging” but the battery level goes down.
• Heat: the phone gets very hot while plugged in.

What are the causes of a charging fault?

1. Dirty charging port: pocket lint or dust in the port stops the cable touching the pins.
2. Bad cable or adapter: USB cables break easily inside. Test with another charger first.
3. Broken charging pins: rough plugging bends the tiny metal pins inside the phone.
4. Battery failure: an old or swollen battery cannot hold power.

Why is a swollen battery dangerous?

• Heat: it can overheat.
• Leaking: it can leak chemicals inside the phone.
• Fire: it can catch fire.
• Action: stop using it and replace it.

What are display faults?

A display fault is a problem with the screen, which is the “window” of the phone, so you cannot see what you are doing.

What are the signs of a display fault?

• Cracked screen: lines running across the glass.
• Black spots: dark “ink” patches that grow bigger over time.
• Ghost touching: the phone opens apps by itself, as if an invisible hand is touching it.
• White screen: the phone is on, but the screen is plain white.

What are the causes of a display fault?

1. Physical pressure: sitting on the phone or dropping it on a hard floor can crack the glass and damage the screen.
2. Water damage: even a little rain can get behind the screen and short-circuit the lights.
3. Loose ribbon cable: a thin ribbon joins the screen to the circuit board. If it is loose, the picture flickers or disappears.

What causes ghost touching?

• Damaged touch layer: a cracked or faulty touchscreen sends touches that nobody made.
• Moisture: water or sweat on or inside the screen confuses the touch layer.

What are sound faults?

A sound fault is a problem that leaves the phone silent or makes the sound weak or poor.

• Volume settings: the volume is turned down or the phone is on silent. Check this first.
• Blocked speaker: dust or dirt covers the speaker opening.
• Faulty audio IC: the chip that controls sound on the circuit board has failed.

What should you check first for each fault?

Check the simple causes first, because they are quick and cost nothing to fix.

How can phone faults be prevented?

Most phone faults come from the way we handle the phone, so careful use prevents many of them.

• Use a protective case: it protects the screen and the internal antenna from drops.
• Do not overcharge: leaving the phone plugged in every night can heat the battery and make it swell.
• Keep it dry: never use the phone with wet hands or in the rain.
• Plug in gently: rough handling bends the charging pins.
• Keep the port clean: keep the phone out of dusty pockets so lint does not block the port.

Evaluation

1. If your phone says “No Service”, what are the first two things you should check?
2. Why should you never use a swollen battery?
3. What is ghost touching, and what causes it?
4. How can dust in a charging port stop a phone from charging?
5. Name two causes of a display fault.

Assignment

Draw a table with three columns: fault area, two signs and two causes. Fill it in for network, charging and display faults.

Teacher’s note

• Practical demonstration: if you have an old, broken phone, open it and show students the charging port and the SIM slot.
• Purpose: let them see how tiny the pins are, so they understand why being rough with a charger causes faults.