Replacement type 700mA high voltage fuse tube for
modern microwave ovens. This high voltage fuse is wired in series with
the high voltage feed from the high voltage transformer to the
The fuse will fail if there is a fault in the high voltage circuit.
Such a fault could be a short circuit magnetron or a short circuit high
voltage rectifier. In our experience however this fuse commonly fails
for no apparent reason.
The fuse just gets stressed everytime the magnetron starts which
eventually leads to the demise of the fuse. The fuse however may also
fail if the microwave cooking cycle is started with no food or metal
objects in the oven cavity.
If you have a microwave with this type of fuse then the symptom you
will get if it has failed is no cooking action. The microwave will
appear to start and countdown time but there will be no heating action.
The fuse is easy to check visibly by unscrewing the fuse housing
apart as shown in the photograph. You can then visually examine the wire
in the fuse to see if it has broken. For the more technically minded a
continuity check with an ohm meter will also check the fuse. A short
circuit reading should be obtained if the fuse is intact.
The fuse can be
replaced as a complete holder assembly though in this case the glass
tube only is offered. This will alow a cheaper and equally as effective
repair. In most instances the glass tube can simply be pulled from the
end caps of the fuse holder.
The fuse holder is opened by twisting each end in opposite
directions. Some high voltage fuse assemblies are smaller and
rectangular in shape but in most cases after clipping apart a fuse tube,
as shown here, is fitted inside. It is not relevant if your fuse tube
does not have the coiled spring inside as ours do.
This is the technical specification of the fuse:
- Current Rating 700mA, 0.7A
- Voltage Rating 5kV/ 5000V
- Overall Length of Fuse Tube: 40mm
- Fuse Tube Diameter: 6.5mm
This type of fuse
is fitted to many brands of microwaves and this particular type of fuse
is suitable for replacement in any brand. Check the rating of the
original fuse and replace with the correct value.
To fit this fuse it is necessary to remove the outer casing so
replacement should only be attempted by those who have experience in the
repair of electrical appliances.
High voltages are present in a microwave oven and it is important
that the appliance is disconnected from the mains before any servicing
work is carried out.