3.5 Installing or Replacing the Appropriate Power Supply
COMPTIA A+ CORE 1 - DOMAIN 3
Cyber Wizard
This article provides guidance on selecting, installing, and replacing power supplies based on system requirements, as required for the CompTIA A+ exam.
CompTIA A+ Exam Domain: Domain 3.5 - Given a scenario, install or replace the appropriate power supply.
Understanding Power Supply Requirements
A power supply unit (PSU) converts AC power from a wall outlet into DC power for a computer system. Choosing the correct PSU ensures system stability and efficiency.
Input Voltage Considerations
110-120 VAC – Standard in North America and some parts of Asia.
220-240 VAC – Used in Europe and many international regions.
Some power supplies have a manual switch for selecting the correct voltage, while others feature automatic voltage adjustment.
Output Voltages
Different components require different voltage outputs:
3.3V – Used for low-power components such as RAM and some motherboard circuits.
5V – Common for legacy hardware, USB devices, and some logic boards.
12V – Powers high-energy components like CPUs, GPUs, and cooling fans.
Power Supply Connectors
Modern power supplies come with various connectors to support different system components.
20-pin to 24-pin Motherboard Adapter – Used to convert older PSUs with 20-pin connectors to work with newer 24-pin motherboard sockets.
SATA Power Connectors – Provide power to SSDs, HDDs, and optical drives.
Molex Connectors – Used for older drives, fans, and some expansion cards.
PCIe Power Connectors – Supply additional power to GPUs and high-performance add-on cards.
CPU Power Connector (4-pin/8-pin EPS) – Dedicated power for processors.
Types of Power Supplies
Different power supplies cater to various computing needs.
Redundant Power Supply
Used in servers and mission-critical systems.
Provides failover support in case of PSU failure.
Ensures high availability and reliability.
Modular Power Supply
Allows users to detach unused cables, reducing clutter and improving airflow.
Available in fully modular (all cables detachable) and semi-modular (only essential cables fixed).
Wattage Rating
Selecting the correct wattage ensures system stability and future expandability.
Calculating Wattage Needs:
Add up the power consumption of all components (CPU, GPU, storage, fans, peripherals).
Use online PSU wattage calculators for precise estimates.
Leave headroom for future upgrades (recommended: 20-30% extra wattage).
Common Wattage Ratings:
300-500W – Basic office PCs, no dedicated GPU.
500-750W – Mid-range gaming and workstation PCs.
750-1000W – High-performance gaming rigs, overclocked CPUs, multiple GPUs.
1000W+ – Extreme gaming setups, servers, cryptocurrency mining.
Installation and Replacement Steps
Check Compatibility – Verify wattage, connectors, and physical dimensions (ATX, SFX, TFX, etc.).
Power Down and Unplug – Disconnect the system from power sources.
Remove the Old PSU – Unscrew and detach cables carefully.
Install the New PSU – Secure it in the case, ensuring proper airflow.
Connect Required Cables – Attach the motherboard, CPU, GPU, storage, and peripherals.
Power On and Test – Ensure stable operation using BIOS and power monitoring tools.
Final Thoughts
Choosing the right power supply is crucial for system performance, stability, and longevity. The CompTIA A+ exam tests knowledge of input voltage, output power distribution, connector compatibility, and power supply types. Understanding these concepts ensures IT professionals can troubleshoot and install power supplies effectively.