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Fusible resistor identification

Discussion in 'Troubleshooting and Repair' started by Wurzel, Sep 2, 2011.

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  1. Wurzel

    Wurzel

    4
    0
    Sep 2, 2011
    Hi
    Trying to check the value of what I think are fusible resistors on the input side of a pcb mounted 230Vac (0-115,0-115 in series) transformer. Each winding is rated at 0.06A. The resistor has for bands which are: brown, black, brown, silver. Colours may have changed due to transformer failure.
    Is there a calculation to help verify its value.
    Any help gratefully received
     
  2. duke37

    duke37

    5,364
    771
    Jan 9, 2011
    This may be a resistor, check with a meter for resistance.
    Brown 1
    Black zero
    Brown 1 (Number of zeros)
    Silver +/- 10%

    So this could be a 100 ohm resistor. If a thermal fuse, 100deg C or perhaps a 100mA fuse.
    A picture would help.
     
  3. shrtrnd

    shrtrnd

    3,816
    518
    Jan 15, 2010
    ... or maybe info on the manufacturer of your board. Some manufacturers like specific
    designs for their power supplies that we'd recognize by model or mfgr.
    Right now we'd be doing a guessing game.
     
  4. Wurzel

    Wurzel

    4
    0
    Sep 2, 2011
    Thanks for the feed back.
    Sorry I don't have a picture at this time. I will look to post. Unfortunately there is no board info.
    There is a device in each leg of the feed to the transformer. Both are open circuit after transformer failure.
    Subject to posting a picture. The resistor looking device is slightly dark sky blue and about the size of a 2W metal film resistor. To be a fusible resistor. Would there be more coloured bands? For example five.
    What purpose would resistor serve in the feed to a transformer? Some sort of ac choke maybe
     
  5. shrtrnd

    shrtrnd

    3,816
    518
    Jan 15, 2010
    It SOUNDS like a simple flameproof resistor. NTE has a wide variety of them.
    The purpose of the resistor is to limit the current.
    I would imagine there is a fuse elsewhere for your transformer input.
    (Look for it. If it's there, your device is probably not a fuseable link).
    If you can't find a fuse, I'm wrong, and maybe your device is acting as a fuse of some type.
     
  6. Wurzel

    Wurzel

    4
    0
    Sep 2, 2011
    Many thanks for that. Yes there is a fuse protecting the transformer.
    I think you are right about it being it a resistor. It possibly looks more like a metal film rather than a metal oxide. At 0.06A, 100R-2W would seem about right.
     
  7. shrtrnd

    shrtrnd

    3,816
    518
    Jan 15, 2010
    You can identify flameproof resistors, by the vent holes they have on the ends where
    the axial leads attach to the resistor.
     
  8. Wurzel

    Wurzel

    4
    0
    Sep 2, 2011
    Thanks. I have checked and there does not appear to be any. I think I'll use a metal oxide film resistor at 2W. I think this will be suitable given the 0.06A transformer primary current.
     
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