Soldering but dont know which wire is it

Discussion in 'Miscellaneous [BG]' started by TOOL460002, Dec 13, 2015.

  1. TOOL460002


    Nov 4, 2004
    Santa Cruz
    Okay, so I am using a Cioks cable, keeping the RCA connector part and removing the other end to put a female 2.1mm barrel jack instead of the stock male plug. I have one very good reason or need.

    One wire is black and one is white. I don't know which to solder to which and can't test aside from on a pedal. If I'm wrong, it will be center positive. If correct, center negative.

    Any idea how to be sure? I don't have good testing equipment, or I could see what direction the flow was and get the polarity that way. Now I'm shooting 50/50. Might just try it on a pedal I dont use and can't sell due to modifications.

    Sorry im new at this. All help is good. I have no clue. Thanks and have a good football sunday all! Go raiders! (No chance...)
  2. Mike_D


    Sep 17, 2013
    If you are serious enough about doing this type of thing to own a soldering iron, you should go ahead and get a multi-tester. They can be had pretty cheap and are invaluable when you need them. With a volt meter you can verify correct voltage and polarity of the completed cable prior to plugging it into your pedal which is worth a lot to me. Without a volt-meter you will need a continuity tester and the spec's of the power supply together to work out the desired result. A continuity tester is something that you can just build with stuff laying around.

    To work this out, you need two pieces of information: polarity of the RCA connection to the supply and color code of the wire to the RCA connector on the cable. If you look at the manual for the power supply (or possibly stenciled on the case) you should be able to find out whether the tip or ring of the RCA connector is negative. Once you know which portion of the RCA connector is negative then you need to figure out whether that corresponds to the black or white wire.

    To check continuity you need to wire up a circuit such that you touch two wires together and something happens (something good, not a fire). For example, take apart a flashlight and connect a wire to the ring of the bulb and tape the other end to the negative connector of battery. When you touch the tip of the bulb to the positive connector of the battery then it should light. Once that is successful, connect the positive battery to the white wire of you cable and then see whether the tip or ring of the RCA connector lights the bulb when touched to it. In this way you can determine whether white or black is the tip (center) of the RCA cable and then use that in conjunction with the polarity information from the power supply to determine whether white or black needs to be the center of your new connector.
    TOOL460002 likes this.
  3. Killed_by_Death

    Killed_by_Death Snaggletooth Inactive

    Multimeters are about $6 at Harbor Freight.
    TOOL460002 likes this.
  4. TOOL460002


    Nov 4, 2004
    Santa Cruz
    Thanks so much sorry for the delay. It'll go great. Now. Will show pics and result when had. You're the best TB! Lol. Thx.
  5. sissy kathy

    sissy kathy Back to Bass-ics Gold Supporting Member

    Apr 21, 2014
    Arbutus, MD
    All you need to test the polarity is a battery and a flashlight bulb. put the battery at the end of the RCA plug with the light bulb next; tape it in place and touch the side of the light bulb with the wires one at a time. The one that lights the bulb is your negative wire. (black should be negative)

    EDIT: Didn't read all of Mike_D's reply TL/DR; so NeVermind.
    Last edited: Dec 19, 2015
  6. As a general rule of electrical thumb, black is usually negative. The only times I've ever come across the opposite is when the original wiring was done wrong. :)
    However in some cases, white will be negative if the other wire is red, as in guitar or mic, or speaker wiring.
    A cheap (or not so cheap if you're into serious electronic work) meter can be your best friend. Analogs (swing pointer) are best for that kind of work. Digitals will work, but you have to watch for the - before the digits.
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