Laptop charger positive and negative wires

Usually [usually], the red one is positive and the black one is negative. The positive should go to the internal pin and the negative to the external surface.

In doubt, have a look at the laptop, it should tell you the polarity of the DC power jack.

Centre-positive is far more common, but by no means guaranteed.

Have a look at the power supply - it should have symbol like the one below showing you the polarity.

This is, of course, assuming that they've stuck to the convention of red wires for positive and black for negative :]

The power circuitry SHOULD have built in protection against incorrect polarity [a simple diode will do it!], again assuming it's been designed correctly.

Antonio1984 wrote:

Usually [usually], the red one is positive and the black one is negative. The positive should go to the internal pin and the negative to the external surface.

In doubt, have a look at the laptop, it should tell you the polarity of the DC power jack.

Antonio is right, the Red cable should connect to the center of the Jack and the black will connect to the metal shield on the top of the Jack.

Regarding what will happen if the polarity is incorrect, worst case scenario the power will fry the laptop. I'd suggest caution, and before you connect it to power check your soldering to ensure the connections haven't come loose again [it happens] and there are no shorts. I'd suggest some heatshrink around the centerpin/red cable to ensure the black and red cannot mix.

On the power brick there will be a small diagram showing which way it is connected. Looks like a C with a dot in the middle and is labelled with positive and negative.

Normally positive is the pin inside and goes to the red wire... normally

JoeWilliams wrote:

Centre-positive is far more common, but by no means guaranteed.

Have a look at the power supply - it should have symbol like the one below showing you the polarity.

You just posted a picture of the less probable scenario, negative inside :]

Antonio1984 wrote:

JoeWilliams wrote:

Centre-positive is far more common, but by no means guaranteed.

Have a look at the power supply - it should have symbol like the one below showing you the polarity.

You just posted a picture of the less probable scenario, negative inside :]

Well done. I was wondering if anybody would spot that. Five house points.

Mike Webb [TheAnticitizen1] wrote:

Antonio1984 wrote:

Usually [usually], the red one is positive and the black one is negative. The positive should go to the internal pin and the negative to the external surface.

In doubt, have a look at the laptop, it should tell you the polarity of the DC power jack.

Antonio is right, the Red cable should connect to the center of the Jack and the black will connect to the metal shield on the top of the Jack.

Regarding what will happen if the polarity is incorrect, worst case scenario the power will fry the laptop. I'd suggest caution, and before you connect it to power check your soldering to ensure the connections haven't come loose again [it happens] and there are no shorts. I'd suggest some heatshrink around the centerpin/red cable to ensure the black and red cannot mix.

As you've might notice on the picture, I have extended the two red wire with a single red wire. Same with the two black wire. Would that be fine?

tablesalt wrote:

Mike Webb [TheAnticitizen1] wrote:

Antonio1984 wrote:

Usually [usually], the red one is positive and the black one is negative. The positive should go to the internal pin and the negative to the external surface.

In doubt, have a look at the laptop, it should tell you the polarity of the DC power jack.

Antonio is right, the Red cable should connect to the center of the Jack and the black will connect to the metal shield on the top of the Jack.

Regarding what will happen if the polarity is incorrect, worst case scenario the power will fry the laptop. I'd suggest caution, and before you connect it to power check your soldering to ensure the connections haven't come loose again [it happens] and there are no shorts. I'd suggest some heatshrink around the centerpin/red cable to ensure the black and red cannot mix.

As you've might notice on the picture, I have extended the two red wire with a single red wire. Same with the two black wire. Would that be fine?

Yes, as long as they are both +and -

JoeWilliams wrote:

The power circuitry SHOULD have built in protection against incorrect polarity [a simple diode will do it!], again assuming it's been designed correctly.

This is comforting. =]

Antonio1984 wrote:

tablesalt wrote:

Mike Webb [TheAnticitizen1] wrote:

Antonio1984 wrote:

Usually [usually], the red one is positive and the black one is negative. The positive should go to the internal pin and the negative to the external surface.

In doubt, have a look at the laptop, it should tell you the polarity of the DC power jack.

Antonio is right, the Red cable should connect to the center of the Jack and the black will connect to the metal shield on the top of the Jack.

Regarding what will happen if the polarity is incorrect, worst case scenario the power will fry the laptop. I'd suggest caution, and before you connect it to power check your soldering to ensure the connections haven't come loose again [it happens] and there are no shorts. I'd suggest some heatshrink around the centerpin/red cable to ensure the black and red cannot mix.

As you've might notice on the picture, I have extended the two red wire with a single red wire. Same with the two black wire. Would that be fine?

Yes, as long as they are both +and -

Thanks.

And thanks to all of you. I will surely update here after I connect it to the power source. =]

If you connect it incorrectly you will release the magic smoke

Put a multimeter on the power supply that plugs into the jack [if it doesn't have a polarity diagram]. That will tell you polarity. [If you read a negative voltage, than the negative side of the meter is the positive.]

Rockn wrote:

If you connect it incorrectly you will release the magic smoke

Have you tried looking at the manufacturers website, they might have this information.

Dear All,

Just an update. My old laptop works now! I have inhaled the magic smoke of the soldering lead but it's worth it.

Thanks to all for your input!Cheers. =]