Session 1: Inside the Machine

A computer is not a collection of independent components; it is a chain where each link depends on the one before it. The power supply converts mains electricity to the low voltages the board needs. The motherboard distributes power and carries the signals between everything. The CPU executes instructions. RAM holds what the CPU is working on right now, and loses it when power goes. Storage — an SSD or a hard drive — holds the operating system and your files permanently. The GPU draws what you see. And BIOS/UEFI is the small firmware that runs first, checks the hardware, and hands over to the operating system.

That chain is why diagnosis works at all. If the power supply is dead, nothing else matters — no lights, no fans. If the motherboard is dead, you may get fans spinning but no display. If RAM is faulty, the machine may power on and then beep or restart endlessly. If storage has failed, the machine starts fine, the fans run, the logo appears, and then it cannot find an operating system. Each failure has a signature, and the signature tells you where in the chain to look.

This is the single most valuable idea in this course: symptoms point to positions in the chain. Beginners open a machine and start swapping parts at random. Technicians look at the symptom, place it in the chain, and go to the most likely link first. That difference is what makes a diagnosis take ten minutes instead of three hours.

The motherboard is a printed circuit board carrying the CPU socket, the RAM slots, the storage connectors (SATA for older drives, M.2 slots for modern NVMe SSDs), the power connectors, the expansion slots, and the rear I/O — the USB ports, network socket and audio jacks you plug things into. It also carries the chipset, which manages traffic between the CPU and everything slower.

Two features on it matter constantly in repair work. The CMOS battery — a small coin cell — keeps the BIOS settings and the system clock alive when the machine is unplugged. When it goes flat, a machine forgets its boot order and shows the wrong date and time, often with a 'CMOS checksum error' or 'date/time not set' message on startup. That is a five-minute fix with a battery that costs a few hundred naira, and it is one of the most commonly misdiagnosed faults by people who do not know it exists.

The other is the front panel header — the small pin block where the case's power button, reset button and indicator LEDs connect. It is fiddly, its pinout varies by manufacturer, and getting it wrong is why a machine sometimes will not power on after a rebuild even though every component is fine. Photograph it before you disconnect it, every time.

The CPU executes instructions, and its speed matters — but for the work most Nigerian users complain about, it is rarely the bottleneck. A ten-year-old CPU still handles browsing, Office and video calls comfortably. RAM holds what is open right now; when it fills, the operating system starts using storage as overflow, which is dramatically slower, and the machine becomes unusable. Eight gigabytes is the practical minimum in 2026; four gigabytes is genuinely painful, and upgrading it is the cheapest large improvement available.

Storage is where the biggest single gain lives. A mechanical hard drive has a spinning platter and a moving head; an SSD has no moving parts and accesses data electronically. The difference is not incremental — it is the difference between a machine that boots in ninety seconds and one that boots in fifteen, and between launching a program in eight seconds and under one. Replacing a hard drive with a SATA SSD is the most cost-effective repair in this entire trade, and it is the recommendation you will make most often.

The combination that matters: a machine that feels slow usually needs more RAM and an SSD, not a new computer. Diagnosing that correctly — and saying so honestly when the machine is genuinely fine — is what builds a reputation. The opposite, telling every customer they need a new laptop, works once and destroys trust permanently.

A laptop contains the same components as a desktop, arranged differently and constrained by heat and space. The CPU and GPU are usually soldered to the board rather than socketed, which means they cannot be replaced — a dead CPU on a laptop is a dead board. RAM may be on removable SO-DIMM sticks or soldered; storage is usually an M.2 SSD or, on older machines, a 2.5-inch drive in a caddy. The battery, the screen assembly, the keyboard and the hinges are all failure points that do not exist on a desktop, and together they account for most laptop repair work.

The consequence for repair work is significant. On a desktop, almost everything is replaceable individually and cheaply. On a laptop, you must check what is actually serviceable on that specific model before you quote, because a customer told 'we will replace your RAM' on a machine with soldered RAM has been given a promise that cannot be kept. Look up the model's service manual or a teardown video before committing.

Heat is the other laptop-specific reality. A laptop's cooling is a small fan and a heat pipe with a limited margin, and dust blocks it. A machine that is slow, loud and hot is very often simply clogged — the CPU reduces its own speed to avoid damage, a behaviour called thermal throttling, which presents as mysterious slowness. Cleaning the fan and replacing the dried thermal paste routinely restores a machine that a customer believed was dying.

A specification tells you what a machine can do, and reading one is a real skill. CPU is described by family, generation and suffix: 'Intel Core i5-8250U' means an i5, eighth generation, and the 'U' suffix means a low-power chip designed for battery life rather than performance. An AMD 'Ryzen 5 5500U' follows the same logic. Generation matters more than the i3/i5/i7 label — an eighth-generation i5 will usually beat a fifth-generation i7, and customers routinely get this wrong when buying used.

RAM is stated as capacity, type and speed: '8GB DDR4-2400'. Capacity is what matters most; the type must match what the board accepts, because DDR3, DDR4 and DDR5 are physically incompatible and will not fit. Storage is stated as capacity and type: '256GB NVMe SSD' is fast; '1TB 5400RPM HDD' is slow and large. Display is stated as size, resolution and panel type: a 1920×1080 IPS panel is far more pleasant than a 1366×768 TN panel of the same size, and the difference is immediately visible.

Learn to translate these into real use, because that is what customers are actually asking. 'Will this run my work?' means: at least 8GB of RAM, an SSD rather than a hard drive, and a CPU from roughly the eighth generation onward. That description covers browsing with many tabs, Microsoft Office, video calls and light design work — which is what almost everyone means.