The motherboard, CPU, RAM, and power supply form the core of any computing system. When any one of these components fails — or begins to fail — the symptoms can range from subtle (a system that runs slightly slower than expected) to catastrophic (a system that will not power on at all). As an IT support technician, your ability to accurately identify which component is responsible for a given symptom is one of the most practically valuable skills you can develop.
This section covers Objective 5.1 of the CompTIA A+ Core 1 exam: Given a scenario, troubleshoot motherboards, RAM, CPUs, and power. Each of the twelve testable symptoms is examined in depth — what causes it, how to isolate the root cause, and how to resolve it.
Before You Begin
Always follow the standard troubleshooting methodology: identify the problem, establish a theory of probable cause, test the theory, implement the fix, verify functionality, and document. This section maps directly to the "test the theory" phase — knowing which symptom points to which component.
Safety First
Before opening any system: power off completely, unplug the power cable, and press the power button once to discharge residual electricity. Wear an ESD (electrostatic discharge) wrist strap grounded to the case. Never touch component contacts with bare fingers. Capacitors on a PSU can retain lethal charge even when unplugged — never open a power supply unit.
When a computer is powered on, the firmware (BIOS or UEFI) runs the Power-On Self-Test (POST) — a series of hardware diagnostics performed before the operating system loads. The POST checks that essential components are present and functional: the CPU, RAM, video card, and keyboard controller.
If the POST completes successfully and the system hands off to the bootloader, you typically hear a single short beep (on systems with a speaker) or no beep at all. If the POST detects a critical hardware failure, it cannot display an error on screen because the display system itself may not be functional yet. Instead, it communicates through a series of audible beep codes.
Beep codes are not universal. They are defined by the motherboard manufacturer or the BIOS vendor. The three most common BIOS vendors are AMI (American Megatrends), Award/Phoenix, and IBM. Always consult the motherboard manual or manufacturer's website to decode beeps accurately. That said, certain patterns are commonly tested:
| BIOS | Beep Pattern | Likely Cause |
|---|---|---|
| AMI | 1 short | POST passed (normal) |
| AMI | 2 short | POST error — check display |
| AMI | 3 long | RAM not detected or seated incorrectly |
| AMI | 5 short | CPU failure |
| AMI | 8 short | Video card / display memory failure |
| Award | 1 long, 2 short | Video card error |
| Award | Continuous | RAM issue or unseated RAM |
| Any | No beep + no display | No POST speaker, or CPU/power failure |
Exam Focus
The exam does not require memorizing every beep code from every vendor. What matters is understanding that beep codes indicate POST failures, that they vary by BIOS vendor, and that you should consult the motherboard documentation. The most commonly tested pattern is RAM-related beeps — multiple beeps or continuous beeping almost always point to a RAM problem.
A proprietary crash screen is a full-screen error message displayed by the operating system when it encounters a fatal, unrecoverable error — typically a kernel-level failure that it cannot safely recover from. The most well-known example is the Windows Blue Screen of Death (BSOD). macOS displays a similar screen called a kernel panic, and Linux shows a kernel oops or panic message in the terminal.
On Windows 10 and 11, the BSOD displays a frown emoji, a brief description, and a stop code (also called a bug check code). The stop code is the most important piece of information — it tells you what type of failure caused the crash. Common hardware-related stop codes include:
| Stop Code | Likely Hardware Cause |
|---|---|
| MEMORY_MANAGEMENT | Faulty RAM, RAM incompatibility, or RAM running at incorrect speeds |
| PAGE_FAULT_IN_NONPAGED_AREA | Defective RAM or failing storage drive |
| IRQL_NOT_LESS_OR_EQUAL | Faulty RAM or incompatible/corrupt driver |
| WHEA_UNCORRECTABLE_ERROR | CPU error, overheating, or overclocking instability |
| CRITICAL_PROCESS_DIED | Corrupt system files, failing storage, or RAM |
| KERNEL_SECURITY_CHECK_FAILURE | Corrupt drivers or RAM errors |
A single, isolated BSOD after a driver update almost always points to software. However, repeated BSODs — especially with different stop codes — strongly suggest hardware failure, typically RAM or storage. The pattern matters as much as the code itself.
Diagnostic Tip
Windows saves crash dump files to C:\Windows\Minidump\. Tools like WinDbg or WhoCrashed can analyze these files to identify the faulty driver or hardware component. On the exam, Event Viewer is the primary tool for reviewing crash logs.
sfc /scannow checks system file integrity. chkdsk /f /r checks the drive for errors that could cause crashes.A blank screen on boot is one of the most ambiguous symptoms because it can originate from several different component failures. The key diagnostic distinction is determining at what point the screen goes blank and whether any other signs of life are present.
First, determine whether the system is receiving power at all. Do the fans spin? Do any LEDs illuminate? Do you hear POST beeps? Each answer narrows the cause significantly.
| Observation | Likely Cause |
|---|---|
| No power at all — fans silent, no LEDs | PSU failure, failed power button, no AC power |
| Fans spin, beeps occur, no display | GPU failure, unseated GPU, monitor cable issue, monitor failure |
| Fans spin, no beeps, no display | No POST speaker, CPU failure, completely dead RAM, or dead motherboard |
| POST screen shows briefly then blank | GPU driver crash, corrupt bootloader, OS issue |
| Blank after Windows logo | Driver issue, not a hardware POST problem |
A system with no power shows absolutely no signs of life: no fans spinning, no LEDs, no beeps, no display. The cause is almost always the power supply unit (PSU), the power delivery path, or a motherboard short circuit.
The PSU converts AC power from the wall into DC voltages used by components. It outputs three main voltages:
Safety Warning
Never open a PSU casing. Capacitors inside can retain dangerous charge levels — up to 400V — long after the unit is unplugged. If a PSU is faulty, replace the entire unit. PSUs are not field-serviceable components.
Sluggish or degraded system performance that develops gradually — or appears suddenly without an obvious software cause — is frequently a hardware problem. The most common hardware culprits are overheating (thermal throttling), insufficient or failing RAM, and a failing storage drive. A failing CPU is less common but possible.
Modern CPUs and GPUs include protection mechanisms that automatically reduce their operating frequency when they exceed safe temperature thresholds. This is called thermal throttling. A CPU that should run at 4.0 GHz may throttle down to 800 MHz when overheating, causing severe performance degradation. The system remains functional but runs significantly slower.
Thermal throttling is often the cause when a system runs fine after a cold boot but becomes progressively slower over time — it gets slower as it heats up. Monitoring CPU temperature with a tool like HWMonitor or Core Temp during a load test will reveal throttling if it's occurring.
Insufficient RAM forces the operating system to use virtual memory — a reserved area of the storage drive used as overflow RAM (the pagefile in Windows, swap in Linux). Because storage drives are orders of magnitude slower than RAM, excessive pagefile usage causes dramatic slowdowns. Signs include constant hard drive activity (thrashing) and very slow application switching.
Failing RAM can also cause performance degradation. A RAM stick with bad cells may cause the CPU to stall waiting for reliable data reads, or the OS may keep those bad pages in reserve and reduce the effective available RAM.
Diagnostic Tools
Task Manager (Ctrl+Shift+Esc) shows real-time CPU, RAM, and disk usage. If RAM is consistently at 90–100% during normal use, the system needs more RAM. If CPU is at 100% but the system is throttling, check temperatures. Resource Monitor (resmon) provides more granular detail.
Overheating is one of the leading causes of hardware failure and reduced component lifespan. Heat is the enemy of all semiconductor components. Understanding the heat path — from the CPU die, through the thermal paste, through the heatsink, into the airflow, and out of the case — helps diagnose and resolve thermal problems systematically.
| Component | Normal Idle | Normal Load | Danger Zone |
|---|---|---|---|
| CPU (modern) | 30–50°C | 60–85°C | Above 95–100°C |
| GPU | 30–50°C | 65–85°C | Above 95°C |
| HDD | 25–40°C | 35–50°C | Above 55°C |
| SSD (SATA/NVMe) | 25–45°C | 40–70°C | Above 80°C |
Exam Focus
The exam frequently presents overheating as the cause of random shutdowns and sluggish performance. Know that the CPU will throttle first (slow down to reduce heat), and if temperatures continue rising, the system will shut down to prevent permanent damage. This is a protection mechanism, not a failure — but the underlying cause (usually a failed fan or dried thermal paste) must be fixed.
A burning smell emanating from a computer is a serious warning sign that requires immediate action. It indicates that a component is either overheating severely or has already suffered electrical damage. The correct response is always to power off the system immediately.
| Smell / Visual | Likely Source | Action |
|---|---|---|
| Acrid, sharp electrical smell | Capacitor failure on motherboard or PSU | Power off immediately; inspect for visual damage |
| Sweet, slightly chemical smell | Burning PCB traces or components | Power off; look for burn marks on motherboard |
| Hot plastic / insulation smell | PSU internal failure or wire touching hot component | Power off; check cable routing near hot areas |
| Dusty/burning dust smell on first boot | Dust burning off heatsinks after cleaning or seasonal startup | Often harmless — monitor; ensure dust is cleared |
| Smell + visible smoke | Active component failure — capacitor, MOSFET, or PSU | Power off and do not power on again until component is identified and replaced |
Important
Never continue to operate a system that smells of burning electronics. Continued operation risks cascading damage — a failing capacitor on a motherboard can destroy connected components. Power off, unplug, and inspect before doing anything else. If you see smoke or the smell is severe, do not plug back in until the damaged component is identified and replaced.
After powering off and unplugging, conduct a thorough visual inspection. Look specifically for:
A system that powers off suddenly without warning — no BSOD, no error message, just an instant cut to black — is exhibiting one of the most hardware-indicative symptoms. Unlike a BSOD, which is a controlled OS response, an instant shutdown bypasses the OS entirely, pointing to a hardware-level trigger.
| Cause | Pattern | Distinguishing Sign |
|---|---|---|
| CPU overheating | Occurs under load; system runs fine after cooling | Shutdown correlates with high CPU usage; temps spike before shutdown |
| PSU failing / underpowered | Occurs under heavy load (gaming, encoding) | Happens when GPU and CPU both spike simultaneously; PSU can't supply enough wattage |
| RAM failure | Random, not load-correlated | Often accompanied by freezes or BSODs before pure shutdowns |
| Failing motherboard | Random, unpredictable | May have accompanying hardware error codes in Event Viewer |
| Software (OS setting) | After Windows Update or setting change | Can be diagnosed by disabling "Automatically restart on system failure" in Windows |
Applications that crash unexpectedly — particularly multiple different applications, or the same application consistently — can indicate hardware-level instability rather than a software bug. The key differentiator is breadth: one specific application crashing is a software problem; multiple unrelated applications crashing is often a hardware problem.
Exam Focus
When the exam presents application crashes as a symptom alongside other symptoms like sluggish performance or random shutdowns, the answer is almost always RAM failure. MemTest86 is the standard tool to confirm. Multiple different applications crashing = test RAM first.
Computers produce several types of sounds during normal operation — fan noise, drive activity sounds, and occasionally a single POST beep. Any new, unusual, or worsening sounds are diagnostic indicators that should be investigated promptly.
| Sound | Source | Meaning | Action |
|---|---|---|---|
| Clicking / ticking (rhythmic) | HDD | Read/write head seeking — can be normal, or early sign of failure. A distinct "click of death" = head failure | Immediately back up data; run S.M.A.R.T. diagnostics |
| Grinding (mechanical) | HDD or fan bearing | Bearing failure in HDD or fan; imminent mechanical failure | Back up immediately; identify which component and replace |
| High-pitched whining | PSU, GPU, or capacitors | Coil whine from inductors under load; capacitor aging | Often cosmetic (coil whine); persistent whine from PSU = investigate |
| Rattling | Fan (debris/loose blade) | Foreign object in fan or loose fan blade; can also be loose case panel | Power off; locate and remove obstruction; tighten panels |
| Loud fan noise (always) | CPU or case fan | Fan control not working; system stuck at max RPM; possibly thermal issue | Check BIOS fan control settings; verify thermal paste |
| Intermittent buzzing | HDD or PSU | Vibration against case; or failing PSU transformer | Check drive mounting screws; evaluate PSU |
Hard Drive Warning
A rhythmic clicking sound from a hard drive — especially the "click of death" (a repeated clicking with pauses) — indicates that the read/write head is failing to find its home position. Data loss is imminent. Stop using the drive immediately and recover data before doing anything else. Running chkdsk on a drive making this sound can accelerate data loss.
Capacitors are small cylindrical components found on motherboards, GPUs, and PSUs. They store and release electrical charge to smooth out power delivery, filter noise, and stabilize voltage. A healthy capacitor has a flat top. A failing capacitor develops a characteristic bulge at the top — this is called capacitor swelling or capacitor plague.
Electrolytic capacitors contain a liquid electrolyte. When they are exposed to excessive heat, overvoltage, or age, the electrolyte degrades and produces gas. Since the capacitor casing is sealed, the gas causes the top to bulge outward. In advanced cases, the top may rupture, releasing a brown, crusty residue on the board. This is called a leaking capacitor.
Conduct a visual inspection under good lighting, looking at the top surface of all cylindrical components on the motherboard. Healthy capacitors have perfectly flat or very slightly concave tops. A bad capacitor shows:
Because capacitors regulate power delivery to the CPU, RAM, and other components, failing capacitors on a motherboard cause a wide range of seemingly unrelated symptoms: random shutdowns, failure to POST, system instability, application crashes, and sluggish performance. When multiple unexplained symptoms occur on an older system, always inspect the capacitors visually.
Repair vs. Replace
Technically, capacitors can be replaced by a skilled technician with soldering equipment. In practice, for most A+ level support scenarios, a motherboard with multiple bad capacitors is replaced rather than repaired. Component-level soldering is outside the scope of the A+ exam. The exam-level response is: identify the bad capacitors visually → replace the motherboard.
If a computer consistently resets its date and time to the same incorrect value every time it is powered on — typically January 1, 2000, or a similarly "reset" date — the cause is almost always a dead or dying CMOS battery.
The motherboard contains a small section of non-volatile memory called CMOS (Complementary Metal-Oxide Semiconductor) that stores BIOS settings: the system date/time, boot order, hardware configuration, and other firmware settings. While the computer is powered off, a small coin cell battery — typically a CR2032 (3V lithium) — maintains power to this memory so the settings are preserved.
When the CMOS battery dies, the BIOS loses its stored settings every time the system is powered off. The most noticeable symptom is the clock resetting to a default date, but other BIOS settings (boot order, custom hardware settings) may also reset.
A CMOS battery typically lasts 5–10 years. In a system used daily, the computer's main power supply trickle-charges the battery and it lasts longer. In a system that sits unused for extended periods, the battery drains faster.
Exam Focus
This is a high-frequency exam question. The symptom is always the same: date and time reset after every power cycle. The answer is always: replace the CMOS battery (CR2032). You may also see it phrased as "BIOS settings keep resetting" — same answer.
Note that a dead CMOS battery is distinct from a software clock drift issue. If the clock loses time gradually while the computer is running, that points to a software or OS issue. The CMOS battery symptom is specifically about the clock (and settings) resetting completely every time the system is powered off.
Final Exam Reminders
CMOS battery = date/time resets after power off. Replace with CR2032.
Multiple app crashes = test RAM with MemTest86 first.
Random shutdown under load = overheating or PSU wattage issue.
POST beep codes = vary by BIOS vendor; consult motherboard manual.
Capacitor swelling = visual inspection; replace the motherboard.
Burning smell = power off immediately; do not continue operating.