Red wire or the black wire?

Discussion in 'The Projects Forum' started by jordanwb, Feb 27, 2009.

  1. jordanwb

    jordanwb Thread Starter Active Member

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    I have an ancient laptop (Toshiba T4400C) that I want to get going. Inside it there are two batteries. One is dead and one I lost. The one that is dead can be rebuilt, I can make a makeshift battery for the one I lost out of AAA batteries instead of AAAA batteries. The battery pack connects to the motherboard with a small connector that goes on only one way. One wire is black and one is red. Would I connect the black wire to the positive and red to the negative or the other way around?
     
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  2. jpanhalt

    jpanhalt Senior Member

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    In DC, red is usually positive and black is negative. Do you have an ohmmeter? If so, the black should be ground, so to confirm the assignment, see if the black lead is connected to the ground plane, attachment screws, etc. on the PCB.

    John

    John
     
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  3. jordanwb

    jordanwb Thread Starter Active Member

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    I touched the black lead of my ohmmeter to ground and the red lead to the red wire. There was a flow for a short period of time (~half a second). I moved the red lead to what would be the black wire and I got continuous flow.
     
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  4. beenthere

    beenthere Retired Moderator

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    The brief conduction through the red lead was due to capacitors charging. The black lead is circuit ground.
     
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  5. jordanwb

    jordanwb Thread Starter Active Member

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    I tried it again, and I got different results. With the black lead to ground and the red lead to the red wire it read 751 ohms but with the red lead to the black wire it read 1 ohm. So would that mean I'd connect the negative of the batteries to the red wire?

    [Edit] The change in results was because before I had it set to read up to 200 ohms, the second time I set it too read up to 2000 ohms, which caused the change of results.
     
    Last edited: Feb 27, 2009
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  6. studiot

    studiot AAC Fanatic!

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  7. jordanwb

    jordanwb Thread Starter Active Member

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