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Power switch went bad. need to know which pins attach to which wires

My HP pavilion a545c had a on/off switch which broke. The spring switch was bad. I had a computer hardware guy replace it but I think he may have put the female pin terminals in the wrong places. Now it doesnt work. How do I Know which wires go to which pins?

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Re: power switch went bad. need to know which pins...

Looking at the front of PC remove the left side panel. Now looking in at the board. There are two rows of pins in the lowest right hand corner of the board. Your PWRSW is your power switch. Its a two pin connector. The ground wire will be black or white. The ground faces to the right & connects at pin 4 counting from right to left. Power switch takes up pin 4&5.
All done. If tech switched the wires by mistake than flip the connector 180*.

Posted on Jan 01, 2008

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This is a well known faulty MB & it is not wise to throw good money after bad. Let it go, I know it hurts but let it go.

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Ms 7500

Orient the motherboard so we are both looking at it the same way;

Processor to the Top, black and white Ram Memory slots to the Right, white PCI slot, and black PCI Express x16 slot to the Left;

Above the white Ram Memory slots, is the 4-pin ATX +12 Volt power cable connector. Whitish, square, 4 socket hole connector.
General example of this power cable, and it's respective connector,

Right next to it is a black header.
The Front Panel header, (Panel1)
This is the pinout,

Scroll down to Dave G's post.

4 pins across one side, 5 pins across the other side.

The side with 4 pins has the pins numbered EVEN.
The side with 5 pins is numbered ODD.

START on the OPPOSITE side of the missing pin.
As you can see there is -> No Pin 10.
The pin on the other end is Pin 2.

Pins 2, 4, 6, and 8. No Pin 10.

Other side;
Pins 1, 3, 5, 7, and 9.

A) Pins 1 and 3 are for the HarDDrive activity LED. (Light)
Pin 1 is for the Positive ( + ) wire.
If the HDD LED is dim when the harddrive is active, switch the wires around.

2) Pins 5 and 7 are for a Reset switch, IF a Reset switch is used.

3) Pin 9 is N/C. Not Connected. Reserved for the factory

4) Pins 2 and 4 are for the Power On LED. (Light Emitting Diode)
Pin 2 is for the Positive ( + ) wire.
If the PWR LED is dim when the computer is on, switch the wires around.

5) Pins 6 and 8 are for the Power On switch.

6) No Pin 10


The above is a PDF file, Illustrated Parts and Service Map, of the HP Compaq DC5850 Desktop PC.

If it doesn't work just by clicking on it, then copy it, and paste it in your browser search bar. Then press the Enter key.

[This is a PDF file. The computer you are using now has Adobe Reader on it, which uses PDF files.

After you click on the link it may take up to 30 seconds, before the first page comes up ]

For additional questions please post in a Comment.


Oct 09, 2012 | Dell HP DC5850 MS-7500 AM2 SYSTEM BOARD

1 Answer

I am looking forthewireing for a hp pavilion xt919

A) Power cables from Power Supply to motherboard:

1) Product information > Product specifications > HP Pavilion XT919 Desktop PC Product Specifications and What Ships in the Box,

2) According to my sources the motherboard is an Asus CUW-AM,

If this indeed holds to be true, scroll the page down, look at the illustration under the Figure 1: Motherboard layout, heading.
Look at number 22 on the right; ATXPWR

Now scroll down to the motherboard photo.
The white connector with two columns of 10 socket holes, to the right of the black Ram memory slots, is ATXPWR.

Proper name is 20-pin ATX main power cable connector, on the motherboard. This is an example of a 20-pin ATX main power cable, and it's respective motherboard connector,

Note in the three photos the Lock on the side of the power cable connector, and the Tab on the side of the motherboard connector.
The Lock operates like a see-saw on a playground.

To remove the power cable the top is squeezed in, and this causes the hooked end of the Lock to come away from the Tab.
When the 20-pin ATX main power cable is deemed to be properly installed tightly to the motherboard, the hooked end of the Lock will be over the Tab.

B) IDE (PATA) harddrive uses a 4-pin standard Peripheral power cable.
So does the Optical Drive/s,

Note the rounded corners when plugging it in.
{Power cable has been misnomered as a 'Molex' power cable. Molex came up with the connector design. The name stuck. Kind of like calling an adjustable open-end wrench a Crescent wrench }

C) Floppy drives and card readers use a 4-pin small Peripheral power cable,

D) Number 6 -> SYS_FAN, is where the Processor fan plugs in.
SYS_FAN stands for System Fan. A computer case fan. The illustration is wrong.

E) Number 21 is PS_FAN.
That to me stands for Power Supply Fan. Another misnomer. The Power Supply has it's own fan, and doesn't need power from the motherboard for it.
I'll bet this is where a System Fan, or computer case fan, would connect.

F) Number 29 points to the Primary IDE connector on the motherboard.
This is where the 40-pin IDE flat ribbon cable, plugs in for the Harddrive.

Number 24, Secondary IDE, is where the Optical Drive's, IDE flat ribbon cable plugs in.

The rectangular connectors for the IDE flat ribbon cables, has a 'bump', or protrusion, on the outside edge towards the middle,

In this photo it is at the top/middle. There are different styles. Square block, or the two piece design shown.
These bumps, or protrusions line up with a cutout.

A cutout on the motherboard connector, or a cutout on the circuit boards for the harddrive, and optical drive.

IF there is no bump, or protrusion;
There is a faint red strip on one side of the IDE (PATA) flat ribbon cable.

The red strip denotes which side Number 1 wire is on. Number 1 wire in the cable, for number 1 pin in it's connector/s.

Here you can see by the pinout above, that for the black Primary IDE connector, and the blue Secondary IDE connector, Number 1 pin is at the Top.
Red stripe on edge of IDE cable will be at the top, when the cable is attached.

When plugging into a harddrive, or optical drive, Number 1 pin ALWAYS goes toward the power cable.
Towards the 4-pin standard Peripheral power cable.
Red stripe will be towards 4-pin standard Peripheral power cable.

H) Number 14 CD_IN is where the audio cable from the MAIN optical drive plugs into. If you have two optical drives only the main, or Primary optical drive audio cable plugs into the motherboard.

I) The front of your computer is the Front Panel.
The area of contact pins on the motherboard, that the main wires from the Front Panel go to, is the Front Panel header.

Under the photo of the motherboard, the pinout for the Front Panel header is shown, though not very legible.
In the illustration the Front Panel header is Number 30 - Panel.

Looking at the pinout, and looking at the actual Front Panel header on the motherboard photo, it looks as though they have the pinout upside down, in relation to how it actually is.

Note in the motherboard photo, the Front Panel header is shown with 5 pins across the Top, then a space, then 4 more pins.
The Bottom row is 10 pins in a row.

In the Front Panel header pinout, they show 10 pins going across the Top. 4 pins going across the bottom, a space, then 5 pins.

Upside down.

I think it should be this way,

Top Row starting on the Left side going towards the Right;
Pins 2, 4, 6, 8, 10, No Pin, 14, 16, 18, and 20.

Bottom Row starting on the Left side going towards the Right;
Pins 1, 3, 5, 7, 9, 11, 13, 15, 17, and 19.

1) Pins 2 and 4 are for a Reset switch, IF a Reset switch is used.

2) Pins 6, 8, and 10 are for the Power On LED. (Light)
This is for a computer that has 'Turbo'
Dual light Power On LED. May have Green and Yellow lights.

Green for 'Turbo', and Yellow for Normal.
Bunch of hooey, really.

'Turbo' mode is the computer operating in a normal mode, and Normal mode really is the computer slowed down.

Pin 10 is for the Negative ( - ) wire.
Pin 6 and Pin 8 are the Positive ( + ) wires. One for the Green side of the Power On LED, one for the Yellow side of the Power On LED.

3) No Pin 12

4) Pins 14, and 16 are for the HarDDrive activity LED. (Light)
Pin 14 for the Positive ( + ) wire.
If the HDD LED is dim when the Harddrive is active, switch the wires around.

5) Pins 18 and 20 are for the Power On switch.

6) Pins 1, 3, 5 and 7 are for an internal speaker. Used to hear BIOS Beep Codes.
Pin 3 is for the Negative wire ( - ), and Pin 7 is for the Positive ( + ) wire.

7) Pins 9 and 11 N/C. Not Connected. (External SMI lead)

8) Pins 13 and 15 are for a Keylock switch.
Some computers have a Keylock. Unlocked the computer will come on.
I -> believe, Not connecting anything to these two pins, is like having the Keylock in the unlocked position.
May be wrong. May have to have a jumper wire across these two pins for the computer to work.

9) Pins 17 and 19 are for a Message LED

HOWEVER, the best method IMHO is to use an LED light, and touch two pins at a time, to see which ones are for the Power On switch.
When the computer comes on, (Power Supply), then you know which pins are for the Power On switch.

Computer running, do not touch those two pins again, and check the rest of the pins.
Computer turns off, and starts again? Restart switch
LED light blinks? Harddrive activity LED
LED light stays on steady? Power On LED.

Finding which two pins are for the Power On switch, also helps tell you where the rest of the pins are, by looking at the pinout on the HP Support page.

Scroll down to Figure 4: Front panel connectors
Same Front Panel header used for this TriGem (Cognac) motherboard.
Clearer though.

For additional questions please post in a Comment.


Oct 02, 2012 | HP Motherboards

1 Answer

Hp palilivon a 1100y lost all power will not come back on i checked all cords power source everything seems to be ok. but no power still?

I'm going to base this solution on two scenarios from the info you have posted.

1) The power to your home/business went out. Now it's back on.

2) The power has been on all along, and the computer quit.

Based on 1) above;

The Power On switch could be bad, or the Power Supply.

A voltage spike could have occurred, and taken out the ATX power on switch.
(A generic ATX Power On switch is around $5. Example, )

A voltage spike could have taken out a power supply that is of low quality, and/or on it's last leg.

The power supply used in an HP Pavilion a1100y desktop computer is of low quality.
Low quality components are used inside.
(Bestec, and Delta are two of the low quality power supply's used by HP in this time frame)

Plus add to the fact that the computer has some age on it, (5 years old?), and could be dirty inside.
Dirt,dust, etc. 'kills' computers and power supply's.

There is a simple test to perform to see whether the problem is the Power Supply, or the Power On switch.
(The Power On switch is located within the plastic Power On button assembly)
If you wish to know how to perform this test please post in a Comment.

Based on 2) above;
The Power Supply is bad.
The test would be either to use a multimeter, and check the three main voltages coming out of the Power Supply,
Substitute the power supply with a KNOWN to be good compatible unit.
(250 to 300 Watt)

(Sometimes access to another known to be good, compatible power supply may be obtained from a computer that is no longer in use. The user has upgraded to a better computer.
Compatible being that the Power Supply has the required Wattage, and required power cables)

[The three main voltages produced by an SMPS (Switched-Mode Power Supply) used by the Pavilion a1100y desktop computer are;

A) 3.3 Volts DC (Orange wire)
B) 5 Volts DC (Red wire)
C) 12 Volts DC (Yellow wire)
In comparison two D cell flashlight batteries produce 3 Volts DC ]

This is HP Support>Pavilion a1100y desktop computer> Motherboard Specifications,

Looking at the motherboard illustration, and photo at the bottom of the page, we can see what power cables are needed for the motherboard;

A) 24-pin ATX main power cable
(Connector on motherboard illustration marked as ATXPWER1. In the photo it is whitish, and has two vertical columns of 12 square socket holes. It is to the Right of the Ram Memory slots)

B) 4-pin ATX main power cable.
(Connector on motherboard illustration is marked ATX12V. It is to the left of the Intel Northbridge chipset - Intel 915GV GMCH.
In the photo it is the whitish square connector with four square socket holes. It is to the Left of the
aluminum finned Heatsink, sitting on top of the Intel Northbridge chipset)

Other power cables needed are;
1) A SATA power cable for the SATA harddrive
2) One or two 4-pin Peripheral (Standard) power cables for the optical drive/s. (CD/DVD drives)

The Processor fan cable attaches to the motherboard. (CPU_FAN)
The computer case fan attaches to the motherboard. (SYS_FAN)

The ATX form factor is used primarily for describing a motherboard.
Form Factor denotes the size, and shape, and power cables for a Power Supply.

The ATX form factor for a Power Supply;
Size: Approximately 6 inches Wide, 5-1/2 inches Long, and 3-1/2 inches Tall.

A $40 ATX power supply with 300 Watts will do just fine. No need to buy an expensive Power Supply based on advertising as a direct substitute.

One example of an inexpensive reliable ATX power supply for a Pavilion a1100y desktop computer,

Has all the power cables you'll need. Actual maximum wattage rating is 350 Watts.

For additional questions or to clarify anything I have stated, please post in a Comment.


Jun 21, 2011 | Motherboards

1 Answer

HP dv9200 not charging battery

there could be a few problems but first off does it run on just the battery or does it always need power? if it always needs power then id take the covers off the bottom of the laptop and check the wires from the conector on the back of the laptop to the battery, and also try giving the pins where the laptop and battery conect the amount of times iv stripped a laptop down and found its a dirty pin is anoying

Sep 25, 2009 | HP Pavilion dv9500 dv9600 and dv9700 FF...

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Acer 5920g no power

Your DC Power Jack is bad, or the area of the motherboard where the DC power jack attaches to, is bad.

The DC Power Jack, is the small port where your AC adapter,(Charger), plugs into.
This is an example of an average DC Power Jack, for an HP Pavilion laptop, not installed in a laptop yet,
If you click on the photo it will enlarge.

The DC Power Jack in the photo is upside down, in relation to how it sits on your laptop's motherboard.
Those flat metal pins shown on top, go down through the motherboard, and are soldered on the other side.

1.Sometimes when the 'charger' plug is in the jack, and is bumped, it can crack the solder joints for the DC Power Jack's flat pins. This makes an intermittent contact. Eventually there is no contact at all.

2.Sometimes it's a bad design of the DC jack, and just from ordinary usage of the user plugging in the charger, and removing it, this can crack the solder joints.

3.Sometimes the small area of the motherboard where the DC power jack is mounted, can crack away from the main body of the motherboard.
To explain:
Crude example;
Envision a laptop's motherboard as having a 1 foot square shape. (It isn't. It's irregular shaped) Now on one side attach a 2 inch square. This 2 inch square, represents the area that the DC power jack is attached to. A 'Peninsula', if you will. There are circuit traces that go along a motherboard. Think of them as Very, flat, thin, strips of copper wire. These 'wires' become stretched, and break as the 'peninsula' cracks away from the main body of the motherboard.

Have the DC Power Jack replaced, or the motherboard.
DC Power Jack cost? About $6 to $8 dollars.
Labor? $100 to $150.
The tech has to completely disassemble the laptop, to just the bare motherboard in hand. Then unsolder the DC power jack, resolder a new one in, and reassemble the laptop.
Motherboard cost? About $150 on up. Depends on where you obtain it. (Ebay?)
Labor? $100 to $200.

Jul 12, 2009 | Acer Motherboards

1 Answer

Wire came loose on pavilion xe 734 that supplie power to hard dir

First of all these wires don't supply power to HDD. These wires are for indicator LEDs on the front
panel of the cabinet. One wire `power sw' is to switch on the system from the power button on front panel. `power led' wire is of the power led on the front panel. All these wires will be connected to the cluster of pins on one corner of the mother board. If you can see it will be indicated & printed near the cluster of pins on the mbd, that which pair of pins is meant for what connector. Try to correlate the names on connector with the print on the mbd.

Jan 06, 2009 | HP Motherboards

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