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Does it matter which node the posi & neg wires connect to on power jack?


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#1 F-1DeskLamp

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Posted 11 November 2017 - 02:31 PM

Power jack hole on this Asus laptop has two nodes to solder the posi and neg wire to, so does it matter which node the neg wire goes to and which node the posi wire goes to? 

 

I don't think so, but I thought more about it, and I better check just in case.


Edited by F-1DeskLamp, 11 November 2017 - 03:26 PM.


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#2 F-1DeskLamp

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Posted 11 November 2017 - 03:26 PM

There.  Shorter post.



#3 JohnC_21

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Posted 11 November 2017 - 03:33 PM

Yes it does. It depends on what the polarity is on the power brick. If the polarity on the power brick has + on the tip you don't want to connect the negative wire of the motherboard power jack to the tip, you want positive.

 

https://electronics.stackexchange.com/questions/33968/how-to-tell-polarity-expected-of-a-dc-barrel-jack



#4 F-1DeskLamp

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Posted 11 November 2017 - 04:20 PM

Thanks.  Well, none of that was on there.  

 

I wound up connecting it and trying it, and it works.  So I assume that the polarity does not matter on there, thus no markings, or I hit it right on the first try.  

I definitely will take more precaution next round.  I'm not sure that this required any "precaution" in the first place though.  



#5 JohnC_21

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Posted 11 November 2017 - 04:38 PM

If you mean there was no markings on the power brick then you could find the polarity of the connector with a multimeter. 



#6 F-1DeskLamp

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Posted 11 November 2017 - 04:51 PM

Sorry, how do I do that?  



#7 JohnC_21

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Posted 11 November 2017 - 05:22 PM

https://www.atbatt.com/laptop-chargers/how-to-test-laptop-adapter

 

If the probes are reversed in the last image on the connector you would read a negative voltage. This would tell you if the center or outside barrel was positive or negative.



#8 mjd420nova

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Posted 11 November 2017 - 08:50 PM

This sounds like it is an AC output, which has no polarity.  Check the adapter itself for the voltage rating, it should indicate whether it is AC or DC with the two flat lines for DC and  a line and a sine wave for AC.



#9 F-1DeskLamp

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Posted 11 November 2017 - 10:10 PM

The power brick says it is an A/C adapter.  It has a wavy line for the input, and it has a straight line and a broken like underneath of the straight line for the output.  Output being what is flowing to the laptop after the power conversion.

 

That broken line under the straight line is like - - -



#10 rqt

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Posted 12 November 2017 - 04:16 AM

"Wavy line for the input" - that indicates AC input

 

"straight line and a broken line underneath the straight line for the output" - tells you that you have a DC output



#11 Platypus

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Posted 12 November 2017 - 05:58 AM

I wound up connecting it and trying it, and it works... I hit it right on the first try.


Correct. You had a 50/50 chance between success and failure probably damaging something. You had good luck.
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#12 britechguy

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Posted 12 November 2017 - 10:32 AM

Most power supplies also have a polarity marking on them in close proximity to the input and output ratings information.  The one on mine is so small that scanning it made no sense, but here's my quick hand drawing of the thing:

 

Attached File  Power_Supply_Polarity_Marking.jpg   38.19KB   0 downloads

 

This indicates that for this power supply the center contact is the positive contact and the outside contact is the negative contact.

 

I have yet to see a laptop (or similar) power supply that isn't AC input and DC output, so the correct polarity is critical.


Edited by britechguy, 12 November 2017 - 10:34 AM.

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