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Old Jan 23, 2009, 06:38 PM
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Kinetikx's Avatar
Daytona Beach, Florida
Joined Jan 2009
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Transformer polarity

I'm trying to charge up an old Husky brand jump starter/12V power supply so I can then use IT to charge batteries in the field. I've got all the parts, but the problem is that the plug (the one that goes into the starter for charging its internal battery) was broken off of the wall wart wire right at the connector. I'm not very electrically inclined but I do have access to a multimeter so I could test to find out which wire is positive. The only problem is that I don't know how to go about doing this

If this makes it any easier one of the wires has some markings: The wire is black with a solid white line interrupted by 7 white dashes- this repeats down the length of the wire. I would assume this is positive but I've assumed incorrectly too many times with electrical stuff and learned a couple painful lessons The other wire is just black.

Also, I know that the inside of the plug is the positive side(diagram on the transformer)- will I have to strip the insulation off the connector to figure out which wire goes to it ? I guess I could attach it randomly and then test with a multimeter but that brings us back to the first paragraph of this post...

I'll probably go through all this trouble and find out that the starter battery is toast

Pictures available if this convoluted story I've written doesn't make sense.
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Last edited by Kinetikx; Jan 23, 2009 at 07:26 PM.
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Old Jan 23, 2009, 07:37 PM
Pompano Hill Flyers
Miami Mike's Avatar
Miami Lakes, Florida, USA
Joined Mar 2003
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I think I have one just like yours, complete with the 7 white dashes on one wire. Mine says "SEL" on the label but even if yours doesn't, it's probably wired the same as mine. I checked and the wire with the seven dashes is positive. It goes to the inside of the plug. The other plain black wire is negative and connects to the side.

To check with a multimeter, set it on DC volts and probe the two wires with the charger plugged into a wall socket. (Don't let them touch!) You'll get about 18 volts. If you see a minus (-) sign on the display, your black probe is connected to plus and your red probe is connected to minus. If you don't see a minus sign, your red probe is connected to plus and your black probe is connected to minus.
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Old Jan 24, 2009, 03:45 PM
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Daytona Beach, Florida
Joined Jan 2009
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Just the kind of information I was looking for, thanks
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