PSU (Power Supply Unit) (P1, P2)

The power supply unit is the black or silver box, sometimes available in multi-colours, that is in the top of your case that has all the cables coming out of the back of it. The box will often have a fan on it in order for it not to overheat. The box runs on AC/DC power which means that the power is good at both short and long power ranges. The AC/DC is split between internal and external power. The Alternating Current is the external power as that is what is brought in from the plug, which provides 110-115V. Internal is the Direct Current which is needed by various components to be powered and often contains either 5 or 12V of power. It is the PSU that converts the AC into DC to allow the computer to work.

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A multi-coloured PSU



The standard connectors are:

·         P1 – This has 20 or 24 pins and provides the motherboard with power.

·         P4 – ATX12V 4 pin provides power dedicated to the CPU but many modern CPU’s require an EPS12V 8 pin as they need more power.

·         4-pin Peripheral – These go into the various disk drives and case fans and have 2 black wires, ground, 1 red wire, +5V, and 1 yellow wire, +12V.

·         Mini-connector – It is a 4 pin connector and is used to supply power to the floppy drive and can be used as an auxiliary connector for AGP cards.

·         Auxiliary power – There are many types of auxiliary connectors which provide additional power if it is needed.

·         Serial ATA – A 15 pin connector that connects to SATA devices and operates at 3 different voltages, +3.3V, +5V and +12V

·         6-pin – Mainly used for PCI express graphics cards that require additional power.

·         6-pin + 2 – Same as a 6 pin although it has an extra 2 pins in case the card needs more power.

·         C14 IEC connector – Is the 3 pin connector that goes into the back of your PSU and goes into the plug socket.

What the different connectors look like

1. In order for you to be able to remove and replace the PSU you must first make sure that you are earthed and that the side of your computer has been removed via the two screws at the back.

2.Secondly you need to first remove the plug out of the back of the power supply.

3. Then you need to disconnect all of the wires that are connected inside your computer that are connected to your PSU.

4. Then you need to lay the computer on its side and remove the screws holding the PSU to the case.

5. Then the PSU simply comes out, and to replace simply follow the removal instructions in reverse.

The screws you need to remove are located here