GSM Audio Section – SS2 Computer Hardware & GSM Repair Lesson Note (Second Term)

The audio section of a phone is the set of parts that let it “speak” and “listen”. It has three main parts: the loudspeaker, the earpiece and the microphone. Each part has a specific job and a specific way of failing. A fault in this section is called an audio fault.

Behavioural objectives

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

• name the three main parts of the audio section of a phone;
• state the job of the loudspeaker, the earpiece and the microphone;
• describe common faults of each audio component and their causes;
• carry out the software, physical and hardware checks when troubleshooting an audio fault;
• explain how to protect a new microphone when soldering.

What is the audio section of a phone?

When we talk about the audio section of a phone, we are talking about how the phone “speaks” and how it “listens”. If you can hear music but can’t hear a caller, or if people can’t hear you when you call them, you are dealing with an audio fault.

The audio section is divided into three main parts: the loudspeaker, the earpiece and the microphone.

What are the parts of the audio section?

The loudspeaker (buzzer)

The loudspeaker is the biggest audio component. It plays your ringtones, music, and the voice of the person you are talking to when you turn on “Speakerphone”.

• How it works: It uses a tiny magnet and a coil to vibrate a thin plastic film. This vibration creates the sound you hear.
• Common faults:
  1. Muffled or “cracked” sound: This happens when iron filings or dust get stuck on the magnet.
  2. No sound at all: The coil inside might be “open” (broken), or the gold contact springs are not touching the motherboard.
• The “Human” side: Have you ever noticed how a phone sounds bad after being at a construction site or a tailor’s shop? That is because metal dust or fabric lint has entered the speaker holes.

The earpiece (receiver)

This is the small speaker at the very top of the phone. You only hear it when you hold the phone to your ear during a call.

• How to identify it: It is much smaller than the loudspeaker. It is usually tucked away behind a fine mesh grill to keep out earwax and dust.
• Common faults:
  1. Low volume: You can hear the person, but it is very faint. Usually, the mesh grill is clogged with dirt or oil from the user’s skin.
  2. Silent earpiece: The earpiece is dead.
• The “Techie” fix: Before replacing an earpiece, try cleaning the mesh grill with a dry toothbrush. Very often, the “fault” is just dirt!

The microphone (mic)

The microphone is the part that “listens” to you. It takes your voice and turns it into electricity so it can be sent to the person you are calling.

• How to identify it: It is a tiny, usually round or square component at the bottom of the phone. If you look closely at the bottom of your phone, you will see a tiny pinhole. That is where the sound enters the mic.
• Common faults:
  1. “I can’t hear you”: The person on the other end says your voice is gone.
  2. Echo or noise: The person says you sound like you are underwater, or there is a loud buzzing sound.
• The “Human” side: The microphone is the most common victim of water damage. Since it is at the bottom, it is the first part to touch water if a phone is placed on a wet table.

How do you troubleshoot audio faults?

When a student is trying to find an audio fault, they should follow this “Checklist of Three”:

1. Software check: Is the phone on “Silent”? Is the volume turned down? Is the phone stuck in “Headphone Mode” (it thinks a headset is plugged in)?
2. Physical check: Is there dirt in the speaker holes or the mic hole? Are the gold pins on the motherboard clean?
3. Hardware check: Use your multimeter on “Continuity” (beep) mode. Touch the two ends of the speaker. If it beeps, the speaker is good. If it doesn’t beep, the speaker is “blown” and needs to be replaced.

Which audio faults have which solutions?

Student practical tip: soldering a new microphone

When soldering a new microphone, be very careful! If you let solder or flux enter the tiny hole on top of the microphone, you will kill it instantly. Always keep the “hole” face down when soldering nearby.

Evaluation

1. Name the three main parts of the audio section of a phone.
2. Why does a phone often sound bad after being used at a construction site or a tailor’s shop?
3. What should you try before replacing an earpiece?
4. Why is the microphone the most common victim of water damage?
5. Describe how to test a speaker with a multimeter, and say what each result means.

Assignment

Draw a table with three columns: component, one common fault, and the fix. Fill it in for the loudspeaker, the earpiece and the microphone.