Trouble replacing home alarm transformer

Discussion in 'General Electronics Chat' started by dyelan, Nov 6, 2015.

  1. dyelan

    Thread Starter New Member

    Nov 6, 2015
    4
    1
    I am attempting to replace the transformer that plugs into the wall outlet for my home alarm. The old transformer has 3 leads on it. I ordered the exact same model from Amazon and the transformer I received has only two leads. The lead for the ground is missing.

    Is the ground necessary or is there a reason it is not present on the newer transformer?
     
  2. dl324

    Distinguished Member

    Mar 30, 2015
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    Can you post pictures of the power supply labels and plugs?

    Wall wart type power supplies are isolated from line voltage, should have a ground, and wouldn't have an earth ground.
     
  3. Hypatia's Protege

    Distinguished Member

    Mar 1, 2015
    2,781
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    If the missing lead is truly ground it may be tied to the core/jacket in the replacement -- if, on the other hand, it's missing a centertap, you've got hold of the wrong transformer...

    Best regards
    HP
     
  4. dyelan

    Thread Starter New Member

    Nov 6, 2015
    4
    1

    Old is the first. New is the second pic
    20151107_124058.jpg 20151107_123957.jpg

    Thanks for the help!
     
  5. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,521
    2,369
    What is the transformer supplying ?
    Max.
     
  6. dl324

    Distinguished Member

    Mar 30, 2015
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    Check for continuity between the center screw and ground connection on the plug. If you have continuity, you can connect the corresponding terminal on whatever you're powering with the grounding screw on the new adapter.

    You could also check the device you're powering to see if it requires the center terminal to be connected.
     
  7. dyelan

    Thread Starter New Member

    Nov 6, 2015
    4
    1
    The alarm panel

    20151107_144542.jpg

    The green wire looks like it goes to the panel the lead is marked earth. To be honest I am not sure how to check continuity.
     
  8. dl324

    Distinguished Member

    Mar 30, 2015
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    Use an ohmmeter to check for continuity from the center screw terminal to the earth ground pin on the plug.

    To be safe, you could run a separate wire from the ground screw on the new adapter to the earth ground connection; and make sure you secure the screw in a properly grounded outlet.
     
  9. MaxHeadRoom

    Expert

    Jul 18, 2013
    10,521
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    Check continuity with the Ohm meter range.
    I would suspect that the only thing that would be reference to earth ground maybe would be any suppresion devices, for this reason it may be prudent to connect the Earth terminal/lead to an Earth Ground.
    Max.
     
  10. dyelan

    Thread Starter New Member

    Nov 6, 2015
    4
    1
    I wanted to thank everyone for taking the time to help me out. Much appreciated!
     
    Hypatia's Protege likes this.
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