Tip & How-To about Computers & Internet

Laptop DC jack how to know if its bad

while most techs will check a DC jack with an ohm meter, checking it the right way will only tell you if it is bad. the wiggle test, with an ohm meter connected will help you out in trouble shooting. Use safety protocols and don't do this if you are not familiar with electricity and its static components, as it could be dangerous. thus said this is what i did.

Everyone knows, that when you get a short in something, that if you wiggle it sometimes the voltage will come back. Well this short may or may not be shorted when you test it with the ohm meter, when it is unplugged. be sure to ground yourself when working with motherboards, chips and components.

So the first thing you can do is tell if the DC jack is loose.
assuming that you cant physically tell there is a problem. (Physical such as loose part on mother board or slighted pin inside DC jack.) Models like the HP 300c have a nice feature with the jack not mounted on the motherboard. this gives more flex to the DC jack, but some people will show you how loose it is, thinking it is mounted on the motherboard, when its design is to be somewhat loose. however it doesn't mean the jack isn't broken.

If you get a Toshiba say MX35 then the jack is mounted on the motherboard and if this is loose sometimes re soldering it to the motherboard will do the trick. However you will still need an ohm meter to verify that the current is flowing correctly through the jack.

On the HP power packs it calls for voltage of 18.5 DC. while this is the correct voltage most of the wall adapters for HP put out slightly more. 18.65-18.75 which is not a problem, you just don't want it lower than the recommended voltage. With the HP DC jack it also has a pigtail on it. this is aprox. 6 inches in length. when using your poles of the ohm meter disconnect this pigtail from the motherboard and check voltage coming through it. You can carefully do this while its connected to the power supply but you will be very close to positive and negative so be careful to not cross or spark them. on the motherboard pigtail you will have 2 red and 2 black you must verify the voltage from each red to each black. this must be the same while it is off the board. (voltage regulators on the MB will take it into the smaller voltages later but at this point they should be the same)
you will now need a friend or clamps. while having the red and black of the ohm meter connected to the pigtail, or touching, you now wiggle the male plug from the wall to the pigtail. if the voltage flexes you may have a short. be certain that the flex didn't come from movement off of the leads to the pigtail part. if it dips in voltage you have found the right part. if it didn't keep looking. the 110 Power supply did you check it to make sure it had the right DC output voltage. is your ohm meter set for say 20 DC (as your looking for 18.5) see if there is a short in the wall plug before the "wall wart or box" is the short in the plug tip?

pigtail end that plugs to motherboard on HP 300c

male jack into the computer

voltage fluxuates when male end is wiggled, male end not shown here....and boy hard to hold and take a photo

this photo below shows the wall jack is putting out correct voltage

and without any flex to the tip of the male jack it would show this

so replacement of the DC jack is now done and back to a working computer.

Posted by on

Computers & Internet Logo

Related Topics:

Related Questions:

1 Answer

Can you check to see if its good or bad?

An Ohm's meter is the best way to tell you if it's bad, obviously no reading at all means it is open ( BAD ) too many Ohm's and it is shorted out ( BAD ). Of Course there is the old fashioned way of testing it. But it doesn't feel very good so I do not recommend it ( apply 12 Volts DC power and wait to see spark ).

May 07, 2014 | Evinrude Johnson OMC 0582508 - Ignition...

1 Answer

toshiba nb100


1) First thing to check is the AC adapter (Charger) power output.
It is 19 Volts (DC)
Suggest use a multimeter to check.
An economical, yet good enough for this test, multimeter, can be purchased for as little as $8 to $12.
Available in a multitude of stores. An auto parts store is but one example.


In the above video ->

-> TOO DANGEROUS. Take the power cord to a pro to test it.
110 to 220 volts will give you a BAD SHOCK to -> FATAL <-
(Can kill you)

For the second part of the test starting at 3:58, it is okay.
You will be testing for 19 Volts -> DC
If the voltage shown is not at least 17.1 Volts (DC), (90 percent),
the AC adapter is no good.

AC adapter checks out?
Then it's time to check the DC Power Jack.
(DC_IN on the laptop. The jack on the laptop you plug the AC adapter into )

2) Remove the Battery. With a non-metallic object, gently see if you can wiggle the center pin of the DC Power Jack around.
ANY perceptible movement means a bad DC Power jack.

Good news is that it is Not soldered to the motherboard. It is attached to wires, that are attached to a small white plug in connector. (DC Power Jack is connected to a harness),


(You can click on the photo to enlarge)

Once removed, you can check it for continuity with the multimeter, set to OHM. (1K)
Or have it checked.

The DC Power Jack harness, plugs into the CN5 connector on the motherboard,


Looking at the motherboard in the photo, you will see two green squares. The middle square is the Processor.

The green square to the right is what I want you to look at. Specifically, the small white connector to the right of it.
(The green square is a chipset. It has a white triangle < pointing to the Top/Right corner)

Put your mouse cursor on the photo. (Magnified view)
Go to the small white connector to the right, of the green square
I indicated above.
Has a small white arrow ( > ) pointing to the Top/Left corner of the white connector.
This is the CN5 connector on the motherboard.

If the DC Power Jack harness is not the problem, then the problem is Power MOSFET's on the motherboard, and or Capacitors.
(Ceramic SMD capacitor/s)

[Just basic info. Pertains to an HP laptop. Just want you to see about Power MOSFET's,

http://mayohardware.blogspot.com/2010/04/important-parts-on-dv6000-and-dv9000.html ]

Choice is yours, whether you wish to have bad electronic components replaced, or replace the motherboard.
May be more feasible for you to replace the motherboard.

Toshiba Netbook PC NB100 Service Manual, (Free. No junk attached),


Go to the subheading -> Mini Notebook. (5th one down)
Left-click on the blue -> NB100

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 file name (NB100) it may take up to 30 seconds, before the first page comes up.

In the Bookmarks menu to the left, click on the + sign to the left of -
Chapter 4.
In the list click on ->
4.7 System Board, DC-IN, RJ-45 Cable and Bluetooth Card

For additional questions please post in a Comment.

Jul 25, 2012 | Toshiba Computers & Internet

3 Answers

advent N270 netbook will not charge. Orange light comes on initially then goes off. Also when I wiggle the plug into the laptop the light flashes on and intermittently.

It sounds like either a bad connection on the motherboard or a broken wire in the adapter making intermittent connection.

1. With the power adapter disconnected, do you have a power light? This would indicate the adapter is good and the plug is questionable.

2. Check your power adapter output with a multi-meter.(be sure to wiggle the wires around) If the power fluctuates, replace the plug.

3. If the power is solid, replace the motherboard connector.

Nov 22, 2010 | Intel Computers & Internet

1 Answer

Problems with the ac smart adapter Hp Compaq 6910p

You could possibly have a loose dc jack.Being able to wiggle it around and getting it to work tells me that the jack is probally going out.That wiggling your doing can cause an arc on your system board,which can short out your board.Stop wiggling your power supply adapter in your dc jack and take your computer to certified repair shop and have your jack checked.Best to rule this out first ,so no damage is done to your board.If you jack test good ,then replace you power supply....Good luck

Apr 08, 2010 | HP Smart Buy- HP Compaq 6910p Notebook PC...

2 Answers

my laptop lenovo 3000 N100 battery has a problem.. therefore i purchased a new battery but the problem with this battery is that when i use the battery it runs the laptop for 10 -15 mins and then with a click sound cuts of the battery supply. m i having aproblem with the battery or it is ainternal circuit problem.

My Dell laptop has a power problem.
The Dell Precision M20 Battery stops charging when I move the power cord on the DC adapter. When I start moving the cord left to right, the power LED light on the front goes on and off and the battery charge LED goes on and off too.
I removed the precision m20 battery and tested the laptop again. The laptop starts fine from the DC adapter when the battery is removed, but as soon as I start moving the power cord the laptop shuts off. It looks like the laptop looses power immediately.
If you have a problem like that, most likely it’s related either to the power adapter or the DC-IN power jack.
First of all, I tested the laptop power ac adapter with a multimeter. The power didn’t cut off no matter how badly I moved the cord. The power adapter output voltage was 15.45VDC all the time. That means there is nothing wrong with the power adapter and most likely there is a problem with with the power socket inside the laptop.
Now I’m going to test the power socket inside the laptop.
In order to access the power socket I had to disassemble the laptop and remove the top cover assembly with the display.
You can find disassembly instructions for many HP, Dell, IBM, Lenovo, Sony and Toshiba laptops in these service manuals and guides.
In the laptop I was fixing (Tecra M2) the power jack is attached to a DC-IN harness and this harness can be unplugged from the motherboard.
As you see, I removed the DC-IN harness from the motherboard, plugged in the power adapter and tested continuity with my multimeter as it shown on the picture.
When the power cord is still, the voltage output is 15.45VDC, the same as on the plug.
But as soon as I start wiggling the plug inside the jack, the power cuts off and voltage goes to 0. It means, the power harness is bad.
The problem was fixed after I replaced the defective DC-IN harness with a new one.
In some laptops the power socket (DC jack) is soldered to the motherboard.
If the battery stops charging when you wiggle the power plug inside the jack, either you have a bad power adapter (test it with a voltmeter) or the power jack is broken or loose.
You cannot simply unplug the jack and replace it with another one. You’ll have to unsolder the old jack and solder a new one back on the motherboard as I described in this post.
If the power jack is not broken but loose (not making good contact with the motherboard) you can resolder the old jack without replacing it with a new one.
If you want to buy a new one,you can see more information from http://www.udtek.com

Feb 18, 2010 | Lenovo 3000 N100 Notebook

Not finding what you are looking for?

771 people viewed this tip

Ask a Question

Usually answered in minutes!

Top Computers & Internet Experts

Doctor PC
Doctor PC

Level 3 Expert

7733 Answers


Level 3 Expert

102366 Answers

David Payne
David Payne

Level 3 Expert

14161 Answers

Are you a Computer and Internet Expert? Answer questions, earn points and help others

Answer questions