Duke DSO 500, Service Manual

Page: 19 / 80

19
HIGH VOLTAGE CAPACITORS
The high voltage capacitors, Figure 6, store the
rectified high voltage (2.5 kVDC) for operation of
the magnetrons.
Location and Access.
The capacitors are located above the top of the
cook chamber at the rear of the oven. The top
and side panels will need to be removed.
Figure 6. High Voltage Capacitors
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
Tools Required
• Flat blade screwdriver to remove top and
side panels
• 5/16 inch nut driver to remove nuts secur-
ing diodes to top of oven
• Ohmmeter to check capacitors
Operational Testing
The capacitors charge whenever the transformer
is operating. The transformers connected to the
diodes for charging the capacitors are powered
from the 208/240 VAC mains supply through solid
state relays K4 and K5 and mechanical relay K6
and K8. Relays K6 and K8 are controlled by the
door safety interlock requiring the oven door to
be closed to provide primary voltage to the trans-
formers. 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 volt-
age to the control board. The interlock function
can be checked by opening and closing the oven
door and observing the rotation of the fan on top
of the stirrer motor.
COMPONENT OVERVIEW