Revision of Practical Work – SS3 Computer Hardware & GSM Repair Lesson Note (Third Term)

Revision of practical work is a hands-on review of the key skills learned in Computer Hardware and GSM Repair. It covers testing with a multimeter, DC power supply and hot air station, the GSM repair steps, computer cleaning and cable crimping, and lab safety. Students practise each task physically, because a skill is learned by doing.

Behavioural objectives

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

• Use a digital multimeter, a DC power supply and a hot air station correctly.
• Follow the GSM repair steps: visual inspection, power test and short-circuit hunt.
• Clean RAM and replace thermal paste on a laptop.
• Arrange the T568B colour code and crimp an RJ45 cable.
• Apply safety and ethical rules in the lab.
• Use the five-step logic (identify, isolate, measure, replace/repair, verify) in a practical exam.

Why is practical work important in ICT and GSM maintenance?

In ICT and GSM maintenance, “knowing” is different from “doing”. You can read a book about how to swim, but you only learn when you get into the water. The same applies to technology. This lesson is a final refresher of the most important physical tasks you have learned over the last three years.

As you prepare for your final exams and your career, remember: a technician is only as good as their last successful repair. The lesson covers three main practical areas, followed by safety and ethics.

Hardware identification and testing

Before you can fix a machine, you must know your tools well. If you use the wrong tool, you will damage the device and lose the customer’s trust.

The three main tools

1. The digital multimeter: This is your “eyes”. You use it to see electricity.
   • Revision tip: Always check your continuity (beep) mode first. If you touch the two probes together and it beeps, your meter is ready.
2. The DC power supply: This acts like a “perfect battery”. It tells you exactly how much current a phone or laptop is “drinking”.
3. The hot air station (blower): Used for removing chips.
   • Revision tip: Never keep the nozzle in one spot. Always move it in a small circle to spread the heat evenly.

What are the GSM repair “golden steps”?

Most phone faults follow a pattern. If you follow these steps, you will find the problem most of the time.

• Step A: The visual inspection. Open the phone and look for anything “ugly”. Is there green crust (corrosion) from water? Is a chip burnt or cracked?
• Step B: The power test. Connect the motherboard to the DC power supply.
  • Reading 0.00A: The “path” is broken (open circuit).
  • Reading more than 1.00A instantly: There is a short circuit (a component is touching ground).
• Step C: The “short” hunt. Use the rosin method. Coat the board with rosin, inject power, and watch which part melts the rosin first. That is your “villain”.

Computer maintenance and networking practical

For computer systems, the most common practical tasks involve speed and connectivity.

Internal cleaning and upgrades

• RAM cleaning: If a computer beeps and refuses to show a picture, the first thing to do is remove the RAM and clean the golden “teeth” with a soft white eraser.
• Thermal paste: If a laptop is getting too hot and shutting down, the paste on top of the CPU has probably dried up. Clean it with alcohol and apply a small pea-sized drop of new paste.

Networking: cable crimping

You must be able to make a straight-through or cross-over cable using an RJ45 connector and a crimping tool.

• Colour code (T568B): Orange-White, Orange, Green-White, Blue, Blue-White, Green, Brown-White, Brown.
• Tip: Make sure the copper wires go all the way to the very end of the plastic plug before you squeeze the tool.

Safety and ethics in the lab

As we revise, we must not forget the human side of our work.

• ESD (static) protection: Your body carries enough electricity to kill a ₦200,000 motherboard. Always touch a metal surface or wear an anti-static wrist strap before you touch a board.
• Data privacy: If you are testing a repaired phone, do not open the gallery. Testing the camera does not mean looking at the customer’s family photos.
• Workshop cleanliness: A professional leaves their workbench cleaner than they found it. Put your screws in a magnet tray so they do not fall on the floor.

What logic should you follow in a practical exam?

If you feel confused during a practical exam, stop and breathe. Then follow this logic:

1. Identify the symptom (what is it doing or not doing?).
2. Isolate the fault (is it the battery, the screen or the software?).
3. Measure (use your multimeter or power supply to confirm).
4. Replace/repair (soldering or swapping parts).
5. Verify (test it three times before you say it is “fixed”).

Evaluation

1. The multimeter challenge: Set your meter to diode mode. Find any scrap board and see if you can find a capacitor that is connected to the ground.
2. The current reading quiz: If a phone draws 0.05A and stops when you press the power button, is the problem hardware or software? (Answer: usually software/bootloader.)
3. The crimp test: Take a piece of CAT6 cable and see if you can arrange the 8 colours in the correct T568B order in under 60 seconds.
4. The diagnosis case: A laptop turns on, but the screen stays black. List three things you would check first.