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Dagnall PCB Mount Transformers

Discussion in 'Electronic Components' started by pbanny, Jun 13, 2007.

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  1. pbanny

    pbanny Guest


    Has anyone else had problems using Dagnall or Clairtronic (same company) PCB
    mount transformers.

    I am getting very frustrated replacing burnt out transformers. Firstly the
    transformers bulge and the plastic case darkens and run noticeably hot.
    Then, I would assume windings start to short and any fuse supplying the
    transformer blow. The rate of failure is currently running at around 12 -
    15% out of the 500 or so after 18months in use.

    The transformers we use are the 14VA types which are split primary and
    secondary, we are running the transformer at around a 50% load factor with
    occasional peaks for about 10 secs to about 80% rating. When there is a
    'burn-out' the blackening only appears in one of the four bobbin segments,
    sometimes one of the primary and sometimes one of the secondary windings.
    This seems to point that it is not overload problem as I would expect to see
    both the primary or secondary windings 'burn' together but so far this has
    never been the case.

    We have approached MGC Electronics who make these transformers in Malta who
    were of little help and are still holding about 100 of our transformers for
    'testing'. We have heard nothing from them for 6 months or more now. We have
    also approached the original suppliers, Farnell, who say they have had no
    other complaints and can only follow the findings of the manufacturer.

    Our solution has been to swap to a similar unit made by Block from Germany,
    of exactly the same VA rating, and so far have swapped around 100 over the
    last year with absolutely no failures whatsoever.

    One of my biggest ever mistakes, the day I chose to use Dagnall for our

    BE WARNED!!!!

    Paul Bannister
    Data Solutions
  2. Hal Murray

    Hal Murray Guest

    One of the failure modes for a transformer is to get a short between
    adjacent wires. That makes a shorted loop. You get one turns worth
    of voltage across the loop which usually means lots of current and
    hence lots of heat. Soon the insulation on adjacent turns breaks
    down and it just gets worse... (Positive feedback.)

    Are you running any voltage spikes that might breakdown the
    insulation? How hot are they normally running?
  3. JeffM

    JeffM Guest

  4. Prepair Ltd

    Prepair Ltd Guest

    Can't see any multi-posting on my news server, where are the other posts?

  5. pbanny

    pbanny Guest

    Hi Hal

    The transformers are currently run with both primaries in parrallel, i.e.
    115v mode, and run from a 110volt UPS system to compensate in case of power

    Good transformers run quite cool at around 10C above ambient, the ambient
    has been monitored and does not exceed 35C even on hot days last summer.

    I have recently been talking with another company who is also having
    problems with Dagnall transformers and from this conversation it seems that
    Farnell are having complaints from many others but will not let on how bad
    the problem really is. I was beginning to think we were the only people
    using this product and having problems, but now a little more releaved that
    it probably is not our circuit design at fault as this other company's
    product is many years old and it is only since swapping to use Dagnall
    transformers that their problems started.

    Paul Bannister
    Data Solutions
    01384 888600
  6. Perhaps worth a word to the standards bodies whose marks these parts carry..?
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