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Fusible resistors queries

Discussion in 'Electronic Repair' started by N_Cook, Jun 18, 2010.

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  1. N_Cook

    N_Cook Guest

    When did they first arrive and do they always have an unusual body colour?
    There is a patent reference to 1977 but when would the first appearance in
    domestic equipment have been ?.
    Resistors that fail open circuit if a designed-in current capacity weak
    point is exceeded , fuse-fashion, not just the thermal limit of the body ,
    so often no overheating discolouration to the body or surrounding board
  2. Phil Allison

    Phil Allison Guest

    ** Genuine "fusible "resistors with specific fuse current ratings are rare
    beasts - the only ones I know of were used by Yamaha in some of their 70s
    and 80s audio amplifiers and were all miniature wire wound types.

    OTOH - what are nowadays laughingly referred to as "fusible resistors" are
    simply "flame proof" resistors - typically ordinary 0.5W & 1W metal film
    types with a high temp, flame proof coating in lieu of the incendiary paint
    coatings normally used.

    ..... Phil
  3. N_Cook

    N_Cook Guest

    Sorry, I should have said fusible resistors otherwise visually
    indistinguishable from conventional 1/3 or 1/2W, MO resistors.
    Grey bodied 1/3W and 1/2W Philips ones in a 1992 Farnell catalogue
  4. N_Cook

    N_Cook Guest

    As far as Philips NFR25 range came in after 1984 and before 1987.
    I was trying to gauge what sort of current surge would knock out a standard
    MO resistor without leaving any trace of overheating versus a proper 1/3W
    fusible resistor if it was likely to be around in 1990.
  5. What's "MO"? Never heard this term applied to resistors before.
  6. Hmm, let me guess at my own question: metal oxide?
  7. Shaun

    Shaun Guest

    Fusistors have been used in test equipment for many years in the input
    section. Fluke uses them in all the meters.
    I know, I've replaced many in the past.

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