Test Laptop AC Power Adapter with Multimeter by Britec

Test Laptop AC Power Adapter with Multimeter by Britec

Let's say your laptop does not start at all. You plug in the power adapter and press on the power button, but the laptop will not react. It's dead and the power or battery charge LED will not light up.

What could be wrong? Is it bad power jack or the motherboard is dead?

First of all, test the AC/DC power adapter with a multimeter. It's possible that there is noting wrong with the laptop and your problem is related to the power adapter.

Need help with your computer?

[SC_musicfan]

Important - When using a multi-meter to check voltage across the adapter, be sure to understand that the "brick" actually functions as a transformer. In other words, it converts AC power from the wall receptacle to DC power because the laptop battery is actually a DC battery.

When checking voltage in the end of cord between the wall receptacle and where it connects to the "brick", be sure to set your multi-meter to ACV (AC Volts). 600V in UK and 200V in the U.S.

If this checks out ok, you will need to reconfigure the multi-meter to check output voltage at the pin connector which is the connector (usually colored) that plugs directly to the laptop. When checking output voltage from the transformer or "brick" be sure to change the setting on the multi-meter to DCV or DC Volts....20V specifically for most meters. After changing the multi-meter to DCV, Insert one prong/lead from the multi-meter into the pin connector and touch the other prong/lead to the outside of the pin connector as demonstrated in the video.

For diagnostics just remember: AC Power before the "brick" / DC power after the "brick".   

[michaeljhintonpiano]

This is such a clear explanation. You got a gift! I want to mention my brother advised me to pay attention to the little linier diagram that has a + on one end a dot in the middle with a C over it and a minus - sign on the other end. Especially when attempting to replace the adapter with something you might have lying around.

[Britec]

That's for the tips and advise Patrick, there is always something I miss.

[Britec]

@jmitservices Yeah that's a El Cheapo Multimeter, I have a fluke model which is real good.

[patricksmith]

Thank you for nice answer, just trying to help make everyones experience as good as I received from your video. Keep up the good work. You are doing a great service sharing with the rest of us "flawed humanbeings". Thanks again.

[hermit]

Blessings brother, the paper clip was exactly what I needed to test the DC on my charger!

[txdave]

Thanks for this video from Texas. Found out that my charger is bad and I didn't have to buy a new laptop. Cheers!

[Britec]

Your welcome, glad it helped you solve your issue.

[Faldinio]

Worthwhile noting that the multimeter has two voltage settings like the one in the video, you need to use the wave icon for AC (mains) and the line with dashed line underneath for DC (after the brick). Be careful checking mains and make sure you don't accidentally touch the prongs or touch them to each other!

[Thrillho]

Good video, however should have clarified that it's AC voltage you are measuring from the wall to the AC/DC power adapter brick, then DC voltage from the AC/DC power adapter brick to the connector that plugs into the back of your laptop. Set your multimeter accordingly. 

[patricksmith]

Dear Britec09
I thank you for your help, as I am just really getting into computer repair. I am an old electronics tech. A comment as a viewer. When setting up a multimeter it would help if you would also point out that you are turning it to AC volts or DC volts and explain when you should do each. Also when you have negative and positive volts you should not move the black lead just go to the negative post and your meter will show it as a negative volt. Thanks again for your help.

[srvuk]

Thanks for the clear information and demonstration.

I'm sure that it will come is use for those wary of using a multimeter with things connected to a live ac socket.

I'd love to see a video showing how you can measure the power being used by a laptop/NUC during varying loads of usage to illustrate that despite an ac adapter having a certain rated usage, that this is the maximum and will not be the actual usage all of the time.

Useful for those wanting to be as energy conscious as possible when choosing their devices.

Thanks for making and sharing this video! You saved me from having to buy a new adapter.

[BJohn]

As always a clear, lucid and informative video. Thx Brian.

[DeanoEssex]

Does it matter what leads you plug into the multi metre I see they have 3 holes to plug in and some of these metres show the red in the top hole and the black in the bottom with the middle hole free, they are the same metre like yours, M-380B but use different combinations with where the leads are plugged in. Does it matter?

[simonmarchese]

Good video - clear, concise yet comprehensive.

[SaminPK]

Thanks. Very informative. How about if there is no pin inside the end connector/ barrel? ie it is just a barrel. Would just inserting the red probe inside it work?

[zxztv]

Nice tutorial brian.

Ive found the output cable often breaks close to the plug or powersupply end, plug end is easy to replace but the psu i end up carefully cutting round the lid seam with a hobby tool and mini grinding disk to gain access.

And after the cable is done then using epoxy resin to seal it back up.

Yes i am a tight sod :-)

[seabreeze]

Nice Video, be careful when testing mains with multimeters, make sure it's set for AC Volts and NEVER Amps. Also watch your fingers with those probes when they are measuring mains!

[melissaso]

Thank you thank you thank you for making this video - now all I have to do is obtain a multimeter to test whether the problem lies in the adapter...