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Rare 18 amp fuse in Panasonic microwave

Discussion in 'Electronic Repair' started by Jack, May 24, 2006.

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  1. Jack

    Jack Guest

    My 2 y/o Panasonic NN-T664 microwave (1300W inverter design) blew a fuse,
    apparently due to the fuse simply wearing out. All else seems normal,
    including door switches.

    The first symptom was loss of display, but unplugging/re-plugging the power
    cord restored that briefly. Then, I removed and reinstalled the original
    fuse and got another burst of life. The fuse was intermittent for a day
    before finally going open.

    The Panasonic factory fuse was an ABC 125/250V 18A ceramic, but I can only
    find 15A or 20A versions in hardware or electronics stores. Even online,
    18A fuses are elusive. Maximum current in this oven is stated as 12.7A at
    1,460 watts. So far the 15A fuse I replaced it with has held up after a two
    days.

    Does anyone know why Panasonic uses a rare 18A fuse (vs. 15A or 20A) and
    how long a 15A fuse should last?

    Jack
     
  2. Ken Weitzel

    Ken Weitzel Guest

    Hi Jack...

    Here's a couple...

    http://www.circuitprotection.ca/MFsearch.php

    Take care.

    Ken
     
  3. Ruediger

    Ruediger Guest

    Response inserted at corresponding lines - sorry for inconveniences
    The lossy display might point out to a worn-out electrolytic capacitor in
    either the power-supply or the control-circuitry
     
  4. GregS

    GregS Guest

    If it were my own, I would use the 20.
    Its funny that the commercial version is only rated about 1300 watts out but
    has higher current input. Different ways of rating power I guess.
    One power rating is hotter than another I guess. The commercial cost
    about 5 times more !!!!!!!!!!!!!!!

    greg
     
  5. Ralph Mowery

    Ralph Mowery Guest

    If the current is only 13 amps or less the fuse should last forever.
    Sometimes they will get 'tired' and just blow. A fuse develops heat and
    melts . When operated near its rated current they just get hot and do what
    I call a 'sag out' after a period of time. As most homes have either a 15
    or 20 amp fuse/braker the fuse in the microwave is almost not needed as the
    house circuit would go about the same time or before if some other devices
    are connected to the same circuit.

    I work for a large complex and we have many kinds of fuses used in our
    equipment. One odd ball is a 63 miliamp fuse for 250 volts. Another is a
    6.5 amp one. A few years back a repersenative from a fuse company put on a
    talk. At one time the fuse company made many kinds and used that as a
    selling point. Now they are telling us that one fuse will replace about ten
    types they used to make. That is now their selling point.

    I would sitck in the 15 amp fuse and if it holds tehn use the micro wave.
    If it blows in a few weeks then go to the 20 amp fuse.
     
  6. Jack

    Jack Guest

    I'm pretty sure in this case the fuse just "sagged" after two years, as
    someone else put it. The display was either on or off, not variable,
    although the green LEDs were always fairly dim from day one (my only
    complaint with the unit). That could be a separate issue.

    Jack
     
  7. Jack

    Jack Guest

    Good point. It's as if Panasonic wants to save the oven just before the
    whole branch goes down! I will put my faith in the 15A fuse.

    Jack
     
  8. Woodward

    Woodward Guest

    Panasonic had an issue with the 18 amp fuses in a series of their microwave
    ovens. The fuses were not up to spec and they would go intermittent or blow
    for no reason. Panasonic recommends the fuse be replaced with a 20 amp
    fuse.
     
  9. James Sweet

    James Sweet Guest


    If it were my own oven, I'd try the 15A first and if that blows use a
    20A. If a short occurs it'll blow that just as fast as the 18A. If this
    is for a customer though I would not go over 18A just because of
    liability issues.
     
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