Maytag 1324704M, Сервисная инструкция

Страница: 16 / 42

Service Information
!
WARNING
To avoid risk of electrical shock, personal injury, or death, disconnect power to oven and discharge capacitor
before servicing, unless testing requires it.
©2002 Maytag Appliances Company
16021520 Rev. 0 15
Proper Handling of Magnetron Tubes
CAUTION
!
A magnetron tube, like a radio or television tube
must be handled with a reasonable amount of care.
When handling a tube, always handle by the housing
only. Use caution not to touch or strike the ceramic
portion at the top. The carton used to ship service
replacement tubes is reusable.
Magnetron Failure Modes
Magnetron failures that have been identified are
generally grouped into categories shown below.
1. Shorted
Air - This is a case where the tube has had the vacuum
envelope destroyed and air has entered the tube.
This will cause internal arcing and high secondary
current if high voltage is applied.
R.F. Capacitors - May short to chassis. This condition
will also cause loss of high voltage.
2. Open Heater (Filament) - Can be determined by a
ohmmeter when transformer leads are
disconnected. Resistance is normally less than one
ohm; filament does not short internally. Any tube
removed should be checked since usage tends to
make the filament more fragile. Later handling and
shipping may open the filament and thereby mask
the true failure mode when checked at the factory.
3. Low Power - Caused by “wearout” of the emission
characteristics of the directly heated cathode.
Symptoms are: (1) tube current will take longer to
get to operating point than a new tube (normally
about 2 - 3 seconds), (2) tube current does not get
high enough to cause the tube to oscillate with
normal line voltage, (3) oven produces low power
into a load, two-thirds or less than normal.
4. Physical Damage - Caused by mishandling of
magnetron tube.
Ceramic
Antenna
Output
Fins
Magnet
Anode
Block
Terminals/R.F. Capacitors
Not Replaceable
Serial Number