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Fast blow vs. slow blow fuse

Discussion in 'Electronic Repair' started by [email protected], Feb 5, 2007.

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  1. Guest

    Looking at fuse how do you tell difference? Thanks.
  2. Arfa Daily

    Arfa Daily Guest

    A fast blow usually has an " F " designator before the value, whereas a slow
    blow or antisurge type usually carries a " T " designator, for " T " ime
    delay - F2.5A or T3.15A for instance. If you look really closely at the
    actual fuse element, you can usually get a good idea of the type. Some
    antisurge fuses are very obvious, having a spring at one end, or a spiral
    wound nature, which may be on a glass fibre string former. Some, however,
    look little different from a 'straight' type, the only giveaway being a tiny
    'blob' in the middle of the wire.

  3. Jim Land

    Jim Land Guest

    wrote in
    Most reliable way is to read the part number on the side of the fuse and
    look it up in the manufacturer's catalog.

    For example, in the USA, MDL-7-1/2 is a 7.5 amp time-delay, AGC-7-1/2 is
  4. Eeyore

    Eeyore Guest

    It's worth pointing out that US fuses are different to the rest of the world.

    You may also find international (IEC) fuses in US gear as described by Arfa.

  5. Guest

    Thanks all. My fuse is blown but element remaining does have a "blob"
    in middle. Marks are on 1 end is current / voltage 4a/125 on other is
    buss gmc ul csa and a "T in a rectangle." What's th "T"? Ideas on what
    type fuse? Thanks. FYI for a TV.
  6. Guest

    Looked on bussman site and found medium time delay. Tried a GMA fast
    acting in set and blew. Think I should get GMC or you think there's a
    ground condition. 1st fuse doesn't look bad...clear glass and alot of
    element left intack.
  7. Arfa Daily

    Arfa Daily Guest

    A time delay fuse is fitted so that it can withstand the inrush current at
    power up. A 'fast' fuse is not a valid replacement, and will blow for no
    other reason than that ... Fit a " T " rated type of the correct value ( 4
    Amps ), and all should be well.

  8. Is this fuse in that Tv you were trying to fix?

    If you're working on a TV I think you're in over your head if you don't know
    the difference between fast and slow blow fuses. I'm not trying to insult
    you, I'm just cautioning you that working on a TV is dangerous!

    - Mike
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