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I have a Toshiba laptop that is no longer receiving power when it's plugged in. How can I tell if problem is in the AC adapter or in the actual laptop?

I could buy a replacement adapter (this is the one), but I don't know if that is actually the problem.

Any opinion on the chances that it is something internal in my laptop or in the AC adapater w/o buying a new adapter?

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Use a flashlight to check the DC socket on the laptop, see if there is visible damage to the center pin, sometimes the DC socket is soldered to the motherboard and the solder joints can break, some laptops have the DC jack separate from the motherboard and are much easier to replace. – Moab Jan 22 '11 at 23:03
Thanks for the answers - sorry I can only choose one! I got a cheap multimeter at Radio Shack and verified the AC adapter is working fine. It's the laptop :( – RichAmberale Jan 23 '11 at 1:08
up vote 1 down vote accepted

Well, it's hard to do a good test, but here are some starting points:

You need a multimeter. Without it, there is nothing you can do. So first step is to plug the supply in and connect probes of the meter to the inner and outer connections of the supply. You should get around 19 V, if I'm reading the info on the site correctly.

If you get good voltage, then it's very likely that it's working correctly. If you want to be sure and know someone good with electronics, you could try putting some load on the supply. The voltage should not change even under load. Still, it could be complicated to make proper resistor network, so don't try it if you don't know what you're doing.

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You could use a 24V 21W auto lamp as a load. – Linker3000 Jan 22 '11 at 22:54
@Linker3000 But it wouldn't be good enough load. The supply should be able to give around 66 W. Maybe 3 lamps in parallel? – AndrejaKo Jan 22 '11 at 23:26

The safest and proper way is to test with a voltmeter. If you don't have one lying around, they can be purchased for ~$15, less than the price of a new adapter and also a handy tool to have around. Any electrician you know will probably have one as well :)

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I'd suggest using a voltmeter / multimeter. You can get inexpensive ones at your local Radio Shack. What you would do is set the voltmeter to 20V and then use the volt meter leads to touch the metal parts of AC adapter connector. Written on the the AC adapter is its voltage output, and the reading you get from the voltmeter should be very close to that value. If you get a reading that's close to zero, that AC adapter is either not working or you're not touching the connector correctly.

Good luck!

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I'd recommend setting it to 200, if the meter is using 20 based scale. The voltage could be a bit higher, if there's no load. – AndrejaKo Jan 22 '11 at 22:07

If you don't have a meter, based on what I've seen on wilderness survival shows, if you've got some steel wool, you can see whether the AC adapter sets it on fire. That'll tell you whether it's getting a charge. Take the advice with some caution though, as it may also fry your AC adapter, no idea, I'm not a EE nor have I ever tried this.

It still won't tell you if the voltage is off (you'll need a meter) or if the connection geometry just got messed up somehow (meter won't help--you'll just need to try a replacement adapter) though.

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My EE colleague says paperclip and a flashlight bulb would be a safer test. – Dax Fohl Apr 23 '14 at 18:09

I agree with the method of testing Adapter with Multi/volt meter but in many cases (if the fault persists in the Adapter) without the load it is meaning less. You certainly need to put a Dummy-Load to get the proper response.

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