DESKTOP COMPUTER TURN ON PROBLEM

Most new power supplies can only be turned on via motherboard signal. That is why you have to plug in the 20/24 pin connector from PS to mo bo. When operating yellow wire is 12 volts and red is 5 volts DC. And black is ground.

Boy, ya got me.

If it was a small square opaque white socket on the motherboard, that a power cable from the Power Supply; had two YELLOW wires, and two Black wires, and plugged into it, I would know what it is,

http://www.playtool.com/pages/psuconnectors/connectors.html#atx12v4

As technology for personal computers advanced, hardware components needed more power.
The motherboard wasn't able to deliver the power needed, so the 4-pin ATX +12 Volt power cable, was brought out.

More power was needed later.
Hardware components demanded more power, than a 4-pin ATX +12 Volt power cable could deliver.

So the 8-pin EPS +12 Volt power cable was brought out,

http://www.playtool.com/pages/psuconnectors/connectors.html#eps8

It CONNECTS to the motherboard. (For motherboards that use one)
NOT to be confused with the 8-pin PCI Express power cable,

http://www.playtool.com/pages/psuconnectors/connectors.html#pciexpress8

This power cable plugs into a GRAPHICS CARD, not the motherboard. Note the color code of the wires.

For a PCI Express expansion slot on the motherboard, for a graphics card; the best the PCI Express slot can deliver is 75 Watts.

The 6-pin PCI Express power cable was brought out next,

http://www.playtool.com/pages/psuconnectors/connectors.html#pciexpress

It is plugged into the graphics card too, and can deliver up to an additional 75 Watts.
Now there is 150 Watts available for the graphics card.

Computer technology advanced, and the 6-pin PCI Express power cable, couldn't deliver the power needed.

Now comes the 8-pin EPS +12 Volt power cable.

The 8-pin EPS +12 Volt power cable by itself, can deliver up to an additional 150 Watts.

Now there is 225 Watts available for a graphics card.
75 Watts from the motherboard, 150 Watts from the 8-pin EPS +12 Volt power cable.

Color code of wires;
1) Orange = 3.3 Volts
2) Red = 5 Volts
3) Yellow = 12 Volts
ALL are DC Voltage

(Two flashlight batteries produce 3 Volts DC)

4) Black wires are Ground wires. Also are known as Negative wires.


This motherboard happen to have a manufacturer name, and Model Number?

Can't find it?
How about the computer manufacturer name, and model number, it came out of?

The model number for a desktop computer, is on the back of the computer, next to the Windows product key; or up on the side of the computer tower.

(The plastic front of a desktop computer is the Front Panel.
Some older computers had a Door in the Front Panel.
The door is opened, and you look inside -> Down, for the model number)

Post back in a Comment.

Regards,
joecoolvette

http://www.playtool.com/pages/psuconnectors/connectors.html

Hmmm, P4 is usually a designation, for a 4-pin ATX +12 Volt power cable,

http://www.playtool.com/pages/psuconnectors/connectors.html#atx12v4

I see though that they have P2 as the 4-pin ATX +12 Volt power cable, and P4 as a SMALL 4-pin Peripheral power cable,

http://www.playtool.com/pages/psuconnectors/connectors.html#floppy

This type of power cable is used on a Floppy Drive, or a Card Reader.
Not a Harddrive, or Optical Drive. (CD/DVD drive)

The Standard 4-pin Peripheral power cable, is used on an IDE (PATA) harddrive, or optical drive,

http://www.playtool.com/pages/psuconnectors/connectors.html#peripheral

Rounder corners on the Top of the plug connector.
Only plugs in, in one direction.

Owner's Manual > Page 109 -
Power Supply DC Connector Pin Assignments

P1 = 24-pin ATX main power cable,

http://www.playtool.com/pages/psuconnectors/connectors.html#atxmain24

P2 shown above - 4-pin ATX +12 Volt power cable

P3, P5, and P6 are SATA power cables,

http://www.playtool.com/pages/psuconnectors/connectors.html#sata

If you have a SATA optical drive (CD/DVD drive), the above is the power cable used.

Uses a SATA data cable,

http://en.wikipedia.org/wiki/File:SATA_ports.jpg

SATA data cable connector on motherboard, is shown below the SATA data cable.

NOTE*
Color does NOT matter

For additional questions please post in a Comment.

Regards,
joecoolvette

Let's take a look at the MSI 990FXA-GD65 motherboard, and I will tell you, AND show you;

http://www.msi.com/product/mb/990FXA-GD65.html

To the right under the bold heading - AMD 990FX chipset based,
there are views of the motherboard.
I would like you to click on the second from the Left view.
(Shows a Top view of the motherboard) It is turned to the Right.

Turn the view 90 degrees to the Left, and this is how it will be sitting in your computer case.
If you move your mouse cursor around on the view, you will see a magnified view of what the mouse cursor is on.

I will do better than this in a moment, and you will download the Motherboard Manual.

A) Requires a 24-pin ATX main power cable. The connector on the motherboard has a Locking Tab.
The power cable's connector has a Lock with a hooked end.

To ENSURE the power cable is plugged in tightly to the motherboard, the hooked end of the Lock, MUST be over the tab on the motherboard connector,

Basic example of a 24-pin ATX power cable, and it's respective connector on the motherboard,

http://www.playtool.com/pages/psuconnectors/connectors.html#atxmain24

In the photo on MSI Support, the 24-pin ATX main power cable connector on the motherboard, is on the bottom of the motherboard under the Blue, and Black ram memory slots. It is Black in color.

B) Requires an 8-pin EPS +12 Volt power cable. This power cable provides the 12 Volt power needed for the motherboard.
(DO NOT confuse it with an 8-pin PCI-Express power cable. More on this later)

On the motherboard JPWR2 should be printed next to it.
In the MSI Support view, it is at the top RIGHT corner of Military Class.
Black in color, 8 socket holes.

Basic example of an 8-pin EPS +12 Volt power cable, and it's respective connector,

http://www.playtool.com/pages/psuconnectors/connectors.html#eps8

The 8-pin EPS +12 Volt power cable was brought out, to replace the 4-pin ATX power cable.
The Yellow wires you see are 12 Volt wires.

The 4-pin ATX power cable has TWO Yellow 12 Volt wires. (And two Black ground wires)
The 8-pin EPS +12 Volt power cable has FOUR Yellow 12 Volt wires.
(And four Black ground wires)

As more power was required from the motherboard, the 8-pin EPS +12 Volt power cable was brought out, to replace the 4-pin ATX power cable.

C) IF, you are using a graphics card, the motherboard requires a 6-pin PCI-Express power cable ALSO.

This power cable provides more power, to the motherboard's PCI-Express x16 graphics expansion slots, (2)

[ To regress for a moment, you have TWO PCI-Express x16 graphics expansion slots, and TWO PCI-Express x1 expansion slots.

The PCI-Express x16 expansion slots are used for a graphics card.
The PCI-Express x1 expansion slots are NOT. They do not require additional power, either ]

NOTE*
1) IF, your graphics card requires an additional power cable plugged into it, USE IT.
Even with a 6-pin PCI-Express power cable plugged into the motherboard.

2) IF, you do not have the additional power cable, from your Power Supply for your graphics card, AND are using a power adapter cable TO the graphics card, make SURE you use the required amount of 4-pin Peripheral power cables, to that power adapter cable.

Look at a 4-pin Peripheral power cable,

http://www.playtool.com/pages/psuconnectors/connectors.html#peripheral

You will see it has ONE Yellow 12 Volt power wire. (Red is 5 Volts, Black wires are Ground wires)

Using a 4-pin Peripheral power cable TO 6-pin PCI Express power adapter cable, the 6-pin PCI Express power cable requires TWO Yellow 12 Volt wires,

http://www.playtool.com/pages/psuconnectors/connectors.html#pciexpress


Short solution?

A) You have to have an 8-pin EPS +12 Volt power cable.
B) Use a 6-pin PCI Express power cable also, if you are using a graphics card.
C) Use the power cable/s needed for the graphics card, IF it requires one.

On the first link above to the MSI Support website, hover your mouse cursor on the Downloads tab.
In the drop down list that appears, left-click on - Manual.

Drop down to the bottom file, and left-click on the blue - E7640v3.2.zip
This is a Zip file. After you click on the file name (E7640v3.2.zip), a small window will come up on the right.

Click on Save File. In the small window to the left that comes up, write down the wording at the top. This is where the zip file will download to.
Desktop, or My Documents, or Downloads.

[ If you are using a computer with Windows 7 on it, it is
Desktop, or Documents, or Downloads ]

Go to where the file is, DOUBLE-click on it. On the far left side click on
Extract all files. Then click on Next, Next, and Finish.
In the last window DOUBLE-click on the file name. (Next to the Adobe PDF icon)

For additional questions please post in a Comment.
Regards,
joecoolvette

Better than Amazon.com Andrew,

http://www.directron.com/ad202.html

Converts two 4-pin standard Peripheral power cables, (Molex) to one female 8-pin EPS +12 Volt power cable.

4-pin Peripheral +12 Volt power cable,

http://www.playtool.com/pages/psuconnectors/connectors.html#peripheral

[ NOTE*
Designated a 4-pin Standard Peripheral power cable, because there is a 4-pin Small peripheral power cable ]

A) 8-pin EPS +12 Volt power cable,

http://www.playtool.com/pages/psuconnectors/connectors.html#eps8


B) Note the difference from an 8-pin PCI Express power cable,

http://www.playtool.com/pages/psuconnectors/connectors.html#pciexpress8

{4-pin Small peripheral power cable,

http://www.playtool.com/pages/psuconnectors/connectors.html#floppy

Used on the older Floppy Drives, and also used on today's Card Readers in desktop computers }

Bad Power Supply.
Weak voltage power rail, or rails.
{There are three voltage power rails.
1) The 3.3 Volt power rail
2) The 5 Volt power rail
3) The 12 Volt power rail}

The flashing Green LED light is one direct indication of this for HP computers.
Usually there is at least enough power to light LED lights, and spin fans, but your Power Supply doesn't even have that much power.

1) All of the LED lights on at once use less than 1 Watt of power
2) EACH fan uses 2 to 3 Watts of power
3) A typical Processor can use 51 to 125 Watts of power.
Depends on what Processor it is.

The HP Pavilion A847C desktop computer has an ATX power supply, with a maximum rated wattage of 250 Watts.

The ATX form factor for a Power Supply refers to it's case size, for one.
5-1/2 inches Long, 3-1/2 inches Tall, and 6 inches Wide
The common type of Power Supply used in over 80 percent of PC computers out there, and readily available all over.


HP Support > Pavilion a847c desktop computer > Main support page,

http://h10025.www1.hp.com/ewfrf/wc/product?product=448706&lc=en&cc=us&dlc=en&submit.y=7&submit.x=5&lang=en&cc=us

Click on Product information in the list
Now click on Product specifications

Finally click on > Motherboard Specifications, PTGD1-LA (Goldfish )

Scroll the page down to view the motherboard illustration and photo.


The replacement Power Supply has to have,

A) A 24-pin ATX main power cable.
In the motherboard photo, view the Ram Memory slots. The long Blue, and Black slots.

To the right of the bottom corner of the Black ram slot (Slot 4) is a whitish connector.
Two columns of 12 socket holes.
This is where the 24-pin ATX main power cable plugs into.
(ATX Power Connector in the motherboard illustration)

Typical 24-pin ATX main power cable,

http://www.playtool.com/pages/psuconnectors/connectors.html#atxmain24

NOTE the Lock Clip on the side of the connector.


B) 4-pin ATX +12 Volt power cable.
At the bottom Left corner of the Processor socket is a whitish square connector.
4 socket holes.
This is where the 4-pin ATX +12 Volt power cable plugs into.
(ATX12V in the motherboard illustration)

Typical 4-pin ATX +12 Volt power cable,

http://www.playtool.com/pages/psuconnectors/connectors.html#atx12v4

NOTE the Lock Clip on the side of the connector.

{The top of the Lock Clip is squeezed in to release it, and is held while the power cable is removed.
Same for the 24-pin ATX main power cable's connector}


C) SATA power cable.
Used for the SATA harddrive

The SATA power cable has 15 pins, and is the longer connector.
The SATA data cable has 7 pins, and is the shorter connector.

IF, the SATA harddrive has provisions for plugging in a SATA power cable, AND a 4-pin standard Peripheral power cable, ONLY USE the SATA power cable.
Otherwise you will burn up the SATA harddrive.

The SATA power cable plugs into the SATA harddrive.
One end of the SATA data cable plugs into the motherboard, and the other end plugs into the SATA harddrive.

Below the ram slots in the bottom Right corner are the SATA headers on the motherboard, that the SATA harddrive plugs into.
The Blue, Orange, Black and White connectors.

Of course the SATA harddrive only plugs into one of them.
Looking at the motherboard illustration you will see they are numbered.
SATA 1, SATA 2, SATA 3, and SATA 4.

IT DOESN'T MATTER which one you plug your harddrive into. (Or any SATA device)
That's the beauty of SATA.
BIOS will find the harddrive.
But for you, it will be easier to keep track of where the SATA harddrive is plugged in, if you just use SATA 1.

Typical SATA power cable,

http://www.playtool.com/pages/psuconnectors/connectors.html#sata


D) 4-pin standard Peripheral power cable.
Commonly referred to as Molex. (Misnomer)

Used for optical drives, Fans, and other associated hardware.

Typical 4-pin standard Peripheral power cable,

http://www.playtool.com/pages/psuconnectors/connectors.html#peripheral


E) 4-pin Small Peripheral power cable.
Used to be commonly used for a Floppy Drive.
For your computer it provides power to the Memory Card Reader.

Typical 4-pin Small Peripheral power cable,

http://www.playtool.com/pages/psuconnectors/connectors.html#floppy

Watch disconnecting, and connecting this connector. You can bend the pins very easily.
SAFETY
WATCH your fingers as the pins are QUITE SHARP!

All of the power cables listed above are standard for today's Power Supply's.

About the Wattage.
A computer ONLY uses the power it needs, and NO more.

If you put a 10,000 Watt power supply in, and the computer only needed 100 watts for what it is doing, it will ONLY use 100 watts.
To wit, if you install a Power Supply with more Wattage than 250 Watts, it will NOT hurt your computer.

If you need guidance in replacing your Power Supply, or recommendations for a Power Supply, please state in a Comment.

Regards,
joecoolvette

(Apologize for being so lengthy)

Test the Power Supply first.

If you have a multimeter, use the Positive (Red) probe lead to connect to the power wire to be checked.
The Negative (Black) lead connects to ANY ground wire. (ALL Black wires are Ground wires)

Three main voltages are produced by a personal computer Power Supply.
1) Orange insulated wires are 3.3 Volt
2) Red wires are 5 Volt
3) Yellow wires are 12 Volt.
(Again, ANY Black wire is a Ground wire)

Or use an economical power supply tester.
One example,

http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=5250576&CatId=5471

You are making a connection from the green Soft Power On wire, to any Ground (Black) wire with that jumper wire.

Using an HP Pavilion A1330E desktop computer for an example,
we can see that the main power cable is a 24-pin ATX main power cable.

This is readily shown by looking at the motherboard,

http://h10025.www1.hp.com/ewfrf/wc/document?docname=c00496280&tmp_task=prodinfoCategory&lc=en&dlc=en&cc=us&lang=en&product=1829044

Scroll down to the motherboard illustration, and the motherboard photo underneath the illustration.

This is the pin-out for a 24-pin ATX main power cable, and connector,

http://www.playtool.com/pages/psuconnectors/connectors.html#atxmain24

The Green wire (Pin 16) is the Soft Power On wire. The other end of the jumper can touch ANY Black ground wire.

1) ALL the lights use less than 1 Watt of power.
2) EACH fan uses 2 to 3 Watts.
3) A typical Processor can use anywhere from 51 to 125 Watts. Depends on what Processor it is.

The three Processor options for the Pavilion A1330E are, (Socket 939 style),

A) AMD Athlon 64 X2 4800+
B) AMD Athlon 64 4000+
C) AMD Sempron 3200+

The Sempron 3200+ can use up to 62 Watts
Athlon 64 X2 4800+, 110 watts, and Athlon 64 4000+ can use up to 89 Watts.

Point?
You have nothing but the motherboard plugged in, and the Power Supply takes a 'nose dive'.
Power LED turns off.

Bad Electrolytic Capacitors in the Power Supply.
Replace power supply.

What causes this?
1) Most computer failure can be attributed to the inside of the computer is dirty, as well as the Power Supply.

When the cooling components of the Power Supply, (Fan, and internal Heatsinks), are clogged, the cooling capacity drops tremendously.

Heat = Wasted Energy

The Power Supply tries to keep up with the call for power, and eventually components inside the Power Supply fail.

A can of compressed air for computers, used on a regular basis as needed could prevent this. (Observe Anti-Static precautions Before placing hands inside computer)

2) Cheap quality power supply.
Saves the computer manufacturer money.

sounds like you need a new power supply. Not too difficult to change yourself. If your not mechanically inclined, take it to your local shop.

Sounds like the switch is out to me or it is mis connected to the motherboard

In most cases this means that your motherboard is fried, but if you can get your hands on another power supply, try plugging it into your board just to be sure.