View Single Post
  #5   Report Post  
Posted to sci.electronics.repair
Ralph Mowery
 
Posts: n/a
Default Rare 18 amp fuse in Panasonic microwave


"Jack" wrote in message
...
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?

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.