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Finding powe supply polarity from the circuit board?

Discussion in 'General Electronics Discussion' started by drbob, Jan 25, 2013.

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  1. drbob


    Jan 25, 2013

    I've been asked to order a new power supply for a device that unfortunately does not indicate the polarity of its 12V DC barrel jack. I would greatly appreciate it if someone here could help me work out the correct polarity (centre pin +ve or -ve)

    I've attached a photo of the circuit board. It looks like a trace runs from the centre pin through a fuse and up to a choke coil, my very limited knowledge of electronics suggests to me that this means positive charge probably flows from the centre pin, is this correct?

    kind regards,


    Attached Files:

    Last edited: Jan 26, 2013
  2. GreenGiant


    Feb 9, 2012
    that looks like it would be center positive, if you notice the ground plane at the top of the picture runs to the side of the plug housing.

    I can't say with 100% certainty, but the fact that there is a fuse right out of the center pin and what looks like a ground plane is attached to the side connection of the DC input pin is a pretty good indicator.

    Do you now have the original plug for this device?
  3. drbob


    Jan 25, 2013
    Unfortunately the original power adapter has been lost. I tried sending an e-mail to the manufacturer but they didn't get back to me.

    Thanks for your input, I think I'll try with a centre positive power adapter.
  4. Rleo6965


    Jan 22, 2012
    I agree with GreenGiant. Its centre +VE. Negative side of Capacitor was soldered on etch of PCB. Follow the trace and this lead you to negative of Plug. See photo.

    Last edited: Jan 26, 2013
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