does this transformer looks toasted

Discussion in 'General Electronics Chat' started by roughrider27, Jun 18, 2016.

  1. roughrider27

    Thread Starter New Member

    Jun 16, 2016
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    Took these pictures of transformer and back of the board from my crown ce4000 amp ,after haVing a fault light.
     
  2. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Certainly looks as if it heated at some time, lift off a secondary feed component, IOW open up the secondary circuit and see if it still gets warm/hot if maybe the transformer rather than the load.
    Max.
     
  3. roughrider27

    Thread Starter New Member

    Jun 16, 2016
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    I will test it later ,last time crown service this amp for a loud popping sound and p went black,but I did notice when I release the board I found a hex bolt under the board that crown must have lost and not remove that could have grounded on something
     
  4. ian field

    Distinguished Member

    Oct 27, 2012
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    It looks more or less normal to me.

    During manufacture, they vacuum impregnated it with lacquer and then baked it hard.

    Toasted transformers tend to blow fuses, or destroy the transistor if they're in a SMPSU.

    The easiest test on a mains transformer is to disconnect all loads from the secondaries and leave it powered for a while - if it gets hot, you've got a dud.

    SMPSU transformers are a bit different - usually the voltage regulation is taken from one of the secondaries, opening that feedback loop makes the PSU go flat out for a split second - then bang!

    SMPSU transformers are best tested out of circuit - there was the Australian DSE shorted turns tester which uses a comparator oscillator to ping the inductance and clock the ringing signal along a shift register. Basically a row of LEDs show how many cycles of ringing it carried on for.

    AFAIK: DSE dropped that side of their business, but the schematic is floating about online and it doesn't use any unobtanium parts.
     
  5. EM Fields

    Member

    Jun 8, 2016
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    1. Have you tested anything?
    2. What test equipment do yo have on hand?
     
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  6. Papabravo

    Expert

    Feb 24, 2006
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    No it does not. It looks like aging and improper flux removal.
     
  7. roughrider27

    Thread Starter New Member

    Jun 16, 2016
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    Right now I only have a multimeter and about to purchase a Tektronix TDS360 to used on the board
     
  8. ian field

    Distinguished Member

    Oct 27, 2012
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    If you have the schematic - check isolation between any secondaries indicated as separate - shorted turns can include another winding if its bad enough.

    Any leakage between the primary and any secondary is a definite fail - the isolation should withstand about 1500V.

    A fault light on probably isn't anything to do with the power transformers - they usually blow the fuse, SMPSU transformer failure is often more spectacular.

    A mains transformer could have an open primary - but then you wouldn't get *ANYTHING* light up - unless it has a separate mains transformer for standby functions.
     
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