Duke DSO 500, Service Manual

Page: 21 / 80

21
MAGNETRONS
The magnetron filament voltage of 4.5 VAC
is supplied from the high voltage transformer
filament winding. The operating voltage of 5000
VDC is provided by the rectified output from the
transformer high voltage winding.
Location and Access
The magnetrons, Figure 7, are located above the
top of the cook chamber at the left and right side
of the oven. The top and side panels will need
to be removed.
Figure 7. Magnetrons
Safety Issues
WARNING
THE HIGH VOLTAGE CAPACITOR RETAINS
THE 2.5 kVDC CHARGE EVEN AFTER THE
OVEN IS DISCONNECTED. THIS CAPACI-
TOR MUST BE DISCHARGED BEFORE
WORKING ON ANY COMPONENTS IN THE
HIGH VOLTAGE AREA.
• Electrical supply of 208/240 VAC to trans-
formers when POWER switch is in ON
position and oven doors are closed
• Capacitors charge to the 2.5 kVDC level
when the high voltage circuit is properly
operating
• The 4.5 VAC magnetron filament supply
is at 2500 V relative to the chassis
Tools required
• Flat blade screwdriver to remove top and
side panels
• 3/8 inch nut driver to remove nuts secur-
ing the magnetrons to top of oven
Operational Testing.
The magnetrons receive filament and high volt-
age from the high voltage transformers. The
transformers connected to the diodes for charg-
ing the capacitors are powered from the 208/240
VAC mains supply through solid state relays K4
and K5 and mechanical relay K6 and K8. Re-
lays K6 and K8 are controlled by the door safety
interlock requiring the oven door to be closed to
provide primary voltage to the transformers. The
door safety interlocks interrupt this supply when
the door is opened. Operation of relays K4 and
K5 require the POWER switch to be in the ON
position to provide operating voltage to the con-
trol board. The interlock function can be checked
by opening and closing the oven door and
observing the rotation of the blade on top of the
stirrer motor.
COMPONENT OVERVIEW