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

In our last lesson, we looked at why phones won’t turn on or charge. Today, we are looking at “Social” faults. These are problems where the phone is on, but it can’t do its main job: helping you talk to and hear other people.

If you can’t hear your friend, or they can’t hear you, or your signal bars are missing, the phone is basically a fancy offline game boy. Let’s learn how to fix that.

The Microphone (The “Voice” of the Phone)

The microphone (Mic) is a tiny component, usually at the very bottom of the phone. Its job is to “catch” your voice and turn it into electricity.

Common Symptoms:

• People say your voice is very “faint” or far away.
• People hear a “scratching” or “hissing” sound when you talk.
• Total silence: They can’t hear you at all, but you can hear them perfectly.

The Fix:

1. The Pin-Hole Test: Look at the bottom of the phone near the charging port. There is a tiny hole. Often, this hole is blocked by dirt, makeup, or oil. Use a very thin needle to gently clear it.
2. Software Check: Sometimes an app (like a voice recorder) is “holding” the mic. Restart the phone first!
3. Replacement: Modern mics are tiny gold squares soldered to the board. If cleaning doesn’t work, you’ll need your Hot Air Station to swap it for a new one.

The Speakers (The “Ears” of the Phone)

Most phones have two speakers: the Earpiece (top, for private calls) and the Loudspeaker (bottom, for music and speakerphone).

Common Symptoms:

• Cracking Sound: The sound is “shattered” or vibrating, usually because the thin paper inside the speaker is torn.
• Low Volume: You can barely hear the person even when the volume is at 100%.
• Magnetic Dust: Because speakers have magnets, they attract tiny metal dust (especially in workshops). This dust stops the speaker from moving properly.

The Fix:

• Cleaning: Use an old toothbrush and a tiny bit of Isopropyl Alcohol to scrub the grill.
• Replacement: Speakers are usually held in by clips or two small springs. They are one of the easiest parts to replace once the phone is open.

Network Issues (The “Signal” Problems)

This is the most frustrating fault for customers. The phone works, but it says “No Service,” “Searching,” or “Emergency Calls Only.”

How the Signal Travels: The signal enters the phone through the Antenna, travels through a Signal Cable, and is processed by the Network IC (Integrated Circuit).

Common Causes:

1. The Antenna Flex: Inside the phone, there is often a long, thin wire (usually black or white) that connects the bottom of the phone to the top. If this wire is loose after a repair or a hard fall, the signal will vanish.
2. The SIM Reader: If the gold pins that touch the SIM card are bent, the phone won’t even know a SIM is inside.
3. Blacklisting/IMEI: Remember our lesson on IMEI? If a phone is reported stolen, the network will block it. The hardware is fine, but the network says “No!”

Dealing with Water Damage

Many network and sound problems start with a small splash of water. Water causes Corrosion (the green stuff that grows on metal).

• The Microphone’s Enemy: Mics have a tiny hole on top. If water enters that hole, the mic is usually destroyed instantly.
• Short Circuits: Water can bridge two paths on the motherboard, making the phone think “Headphones are plugged in” even when they aren’t. This will disable your speakers.

The Professional Solution: Don’t use rice! Rice doesn’t stop corrosion. Open the phone, remove the motherboard, and scrub the affected areas with Isopropyl Alcohol and a soft brush.

Testing Your Repairs

Once you think you’ve fixed a sound or network fault, you must test it properly before giving it back to the customer.

1. The Echo Test: Call a service number or record your own voice using the “Voice Memo” app. This tests the microphone.
2. The “112” Test: Even without a SIM card, a healthy phone should be able to “see” the network for emergency calls. If it says “No Signal” even on 112, the antenna or Network IC is broken.
3. Toggle Airplane Mode: Sometimes the software just needs a “kick” to go out and look for the towers again.

Quick Diagnosis Guide

Class Activity:

1. Use a magnifying glass to look at the microphone hole on your own phone. Is it clean?
2. Open a “scrap” phone and find the black/white antenna cable. Trace it from the bottom to the top.