Duke DSO 500, Service Manual

Page: 23 / 80

23
MAGNETRON THERMAL
SWITCHES
The magnetron thermal switches, Figure 8, are
used to monitor the magnetron temperature and
open the high voltage supply when the tempera-
ture exceeds 150°C.
Location and Access
The magnetrons thermostats are located on the
side of each magnetron. The top and side panels
will need to be removed.
Figure 8. Magnetron Thermal Switches
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
• 3/8 inch nut driver to remove nuts secur-
ing the magnetrons to top of oven
Operational Testing
The thermostats are connected in the high volt-
age transformer primary circuit and are normally
closed connecting primary voltage on wires 26
and 27 to the high voltage transformer. If mag-
netron is not operating check continuity across
thermostat terminals.
COMPONENT OVERVIEW