PC Power Supply

B142-Lab Assessment Sheet

Student Name: Jessica Rush     

Assessment Topic: The Power Supply

 

	·         Not all PCs are the same.
	·         Make sure you disconnect your PC from the mains electricity supply before you start
	·         As an added precaution, you might also consider using a grounding strap, also sometimes called an anti-static wrist strap. A grounding strap can help to prevent damage to your computer due to electrostatic discharge (ESD) by safely grounding you while you work on your computer.

Getting Started: TOOLS

ü  Philips-head screwdriver

ü  Multimeter  

         

                                               

General Information: 

How do you know whether your PC power needs to be replaced?

            Some signs that your power supply has failed, or may be on its way to failing are:

• There is no power going to your computer or to any of its internal peripherals
• There is a burning smell coming from the power supply
• It’s difficult to turn on your computer, (it takes several pushes of the on/off button for the computer to boot.)
• Intermittent  beep codes and errors occur while booting
• System freezes while booting but after several tries it boots successfully
• System hangs for no reason
• Failure to power on.
• General instability.
• Rebooting, either erratically or when the computer is strained.
• Hardware failure, due to sudden power spikes/dips or long term electronic noise.
• Inability to boot up even though motherboard light is lit. At power on, there is no activity at all except for fans and disks starting to spin.

Removing the faulty Power Supply Unit:

Shut down your PC:

	Left click on the start button
Left click on Shut Down
	Remove Thumb screw located on the rear of the case
Remove case cover.
	Restart your computer

Test the power supply unit using a multimeter:

1. Testing the multimeter:

Plug probes in. Red probe plugged into the VmA hole and the  Black probe plugged in to the COM hole
	Set range dial to ohms
	Touch tips of probes together. The reading should change from infinite (1) to zero (0)

Set range dial to 20V DC (DCV)
	Place Black into a black ground wire, and place the red into the white, red, blue, yellow, and orange wires.

2. Testing the 24-pin ATX power connector:

Voltage	Acceptable Ranges	Your Reading	Wire Color	Within Range? Y or N
-5	-4.5 to –5.5	-4.91	White	Y
+5	+4.5 to +5.5	5.18	Red	Y
-12	-10.8 to –13.2	-11.62	Blue	Y
+12	+10.8 to +13.2	12.00	Yellow	Y
+3.3	+3.0 - +3.63	3.37	Orange	Y

Shut down computer
	Flip main power switch on rear of case and remove AC power connection
	Disconnect the power supply connection from the drives and mother board.

NOTE: POWER SUPPLY CONNECTIONS

Typically, power supplies have the following connectors:

PC Main power connector (usually called P1): Is the connector that goes to the motherboard to provide it with power. The connector has 20 or 24 pins. This connector is the largest of all the connectors. In older AT power supplies; this connector was split in two: P8 and P9. If you have a power supply with a 24-pin connector, you can plug it into a motherboard with a 20-pin connector. In cases where the motherboard has a 24-pin connector, some power supplies come with two connectors (one with 20-pin and other with 4-pin) which can be used together to form the 24-pin connector.
4-pin Peripheral power connectors (usually called Molex for its manufacturer): These are the other, smaller connectors that go to the various disk drives of the computer. Most of them have four wires: two black, one red, and one yellow.
	4-pin Berg power connectors (usually called Mini-connector): This is one of the smallest connectors that supply the floppy drive with power.
Auxiliary power connectors: There are several types of auxiliary connectors designed to provide additional power if it is needed.
	Serial ATA power connectors: a 5-pin connector for components which use SATA power plugs.
6-pin Most modern computer power supplies include 6-pin connectors which are generally used for PCI Express graphics cards. Each PCI Express 6-pin connector can output a maximum of 75 W.
	A C14 IEC connector with an appropriate C13 cord is used to attach the power supply to the power main.

Removing the power supply:

Unscrew the power supply unit from the back of case.
	Remove the power supply from the case
Replace new power supply
	Replace screws

Reconnect all power connections

PC Main power connector (usually called P1)
4-pin Peripheral power connectors (usually called Molex for its manufacturer)
	4-pin Berg power connectors (usually called Mini-connector)
Auxiliary power connector
	Serial ATA connector
6-pin pci express connector
	A C14 IEC connector

Finishing touches

 

Replace case cover
	Secure thumb screw
Reconnect AC power cord, Flip main power switch on rear of case
	Restart computer

 Observe signs that computer is working correctly:

- Power light comes on

- Keyboard lights come on

- Drive lights

- Beeps and chirps

- Test CD-Rom by opening and closing caddy

- Floppy drive lights

- Etc…

 

If you had to do some troubleshooting, briefly state what the problem was and your solution for it.

Assessed by: ___________________________                     Date: _______________

Assessed by: ___________________________                     Date: _______________

Better. The second half doesn’t work well as a follow-along manual. There are a bunch of pictures of items but it it’s hard to find the narrative as to what to do with them – and there are some ends that don’t pertain to what needs to be connected in the class computers.

Score = 28