Practical -75 :-Identification and Assembly of Motherboard Components and Powe Supply

 

AIM :- Identification and Assembly of Motherboard Components

1. Objective

To identify major motherboard components (Northbridge, Southbridge, BIOS, etc.) and perform a complete assembly of power supply (SMPS) and system panel connections.

2. Required Tools & Components

• Hardware: ATX Motherboard, SMPS (Power Supply), CMOS Battery (CR2032).

• Cables: 24-pin ATX, 4-pin 12V CPU, System Panel Cables (Power/Reset/LEDs).

• Safety: Antistatic wrist strap or grounded work surface.

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3. Key Component Reference

Before assembly, locate and identify these parts on your board: 

Component	Visual Identifier	Primary Function
CPU Socket	Large square with a locking lever.	Houses the processor (The Brain).
Northbridge	Chip near CPU with a large heatsink.	Manages high-speed data (RAM & Graphics).
Southbridge	Smaller chip near SATA/IDE ports.	Manages I/O (USB, Hard Drives, Audio).
BIOS Chip	Small chip labeled "ROM" or "BIOS".	Contains boot instructions for the system.
Inductors	Copper coils (Electromagnetic coils).	Filters power and removes voltage spikes.
DDR DIMM	Long slots with clips on the ends.	Holds System Memory (RAM).

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4. Step-by-Step Practical Procedure 

Phase 1: Preparation & Safety

1. Ensure the SMPS is unplugged from the AC wall outlet.

2. Wear your antistatic strap to protect sensitive chips like the BIOS and Northbridge from static discharge.

3. Place the motherboard on a non-conductive surface (like a rubber mat or the box it came in).

Phase 2: Power Supply (SMPS) Connections

1. Main Power (24-Pin ATX): Take the largest cable from the SMPS. Align the plastic clip with the notch on the motherboard’s ATX Power Connector. Press until it "clicks."

2. CPU Power (4-Pin/8-Pin 12V): Locate the smaller square power connector near the CPU socket. This provides dedicated power to the processor via the nearby Inductors. Plug this in firmly.

   Note: If this is skipped, the PC will turn on but will not show any display (No POST).

Phase 3: System Panel (Front Panel) Wiring

These small cables connect the case buttons to the motherboard headers (usually located at the bottom right).

1. Power SW (Switch): Connect to the "PWR_BTN" pins. This allows the front button to turn the PC on.

2. Reset SW: Connect to the "RESET" pins.

3. HDD LED & Power LED: Match the Positive (+) and Negative (-) pins.

   • Tip: The colored wire is usually Positive (+); the white/black wire is Negative (-).

   • Refer to the diagram below for standard pin numbering:

Pin Number	Assignment	Pin Number	Assignment
1 & 3	HD LED (+ / -)	2 & 4	Power LED (+ / -)
5 & 7	Reset SW	6 & 8	Power SW

Phase 4: Final Inspection

1. Check if the CMOS Battery is seated properly to maintain BIOS settings.

2. Ensure no cables are touching the cooling fans.

3. Verify that the RAM is fully clicked into the DIMM slots.

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5. Observation Table

Connection Task	Completed (Yes/No)	Observation (Click/No Click)
24-Pin ATX Power
4-Pin CPU Power
Power Switch (SW)
HDD LED (Polarity)

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6. Viva / Review Questions

1. What is the specific function of the Inductor coils near the CPU?

2. If the computer turns on but the "Power Light" on the case does not glow, what is the likely cause?

3. Which "Bridge" chip connects the CPU to the RAM and AGP/PCIe slots?