AC/DC supply. Identify AC in and DC out?

Discussion in 'General Electronics Chat' started by frascati, Dec 13, 2012.

  1. frascati

    Thread Starter Member

    Jun 1, 2010
    I've got a drawer full of spare power supplies for various projects. All are AC in. Most are SMPS. Most are AC/DC. A few are AC/AC. A few are stacked plate transformers.

    A few of them have the plastic bodies removed.

    How do I identify the AC inputs and DC outputs either visually or with a meter and without risking damage?
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
    The AC input side will have a transformer connected to it usually, or it may go to a filter then bridge rectifier and large smoothing electrolytic capacitor usually 300v/480v rated 220uF/470uF for smpsu.

    the output will have low value dc say 16v to 25v capacitors
  3. panic mode

    Senior Member

    Oct 10, 2011
    1. read the label

    2. use continuity check (when unit is not powered), AC versions are just a transformer so you will get continuity (low resistance) on both input and output (specially on the output)

    3. when it is powered measure output using multimeter in both AC and DC range

    4. if they are open, you can just look and tell. AC will only have a transformer. DC will have diodes and polarized electrolytic capacitor(s).