21
Service Manual for
RCO Speed Oven
Operational Testing
The Magnetron Cooling Fan operates constantly when
the oven is connected to its power source. It provides
cooling for both the Magnetrons and the High Voltage
components. If not operating, the line fuse should be
checked. Inspect all wiring between the fuse holder
and the fan. Test the motor winding leads for a short,
open, or grounded condition.
Magnetron Cooling Fan Replacement
1. Remove the unit from its power source and follow
the proper Lockout/Tagout procedures.
2. Remove the rear service panel.
3. Observe all High Voltage cautions and warnings.
4. Tag and disconnect the Magnetron Cooling Fan
wires.
5. Remove the Magnetron Cooling Fan assembly.
6. Remove the cooling duct assembly and attach it to
the new cooling blower.
7. Install the new Magnetron Cooling Fan assembly.
8. Referring to the tags, reconnect the fan wires.
9. Briefly restore power to the unit, the Magnetron
Cooling Blower should operate as soon as power
is restored.
10. Remove the unit from its power source and reattach
the rear service panel.
11. Restore the unit to its power source and ensure it
is operating properly.
MAGNETRON THERMAL SWITCHES
The High Voltage Capacitor
retains a 2.5kV DC charge after the oven has
been disconnected from its power source. The
capacitor must be properly discharged prior
to beginning work on any components in
the high voltage area. Failure to comply can
cause property damage, injury or death. Refer
to the Discharging the High Voltage System
section of the manual for proper instructions
for this procedure.
Hot Surfaces. The Magnetron
housings may be hot.
Magnetron
Thermal Switches
Location of Magnetron Thermal Switches
Operational Testing
The Magnetron Thermal Switches are connected in
series with high voltage transformer primary circuit and
are normally closed conducting primary voltage to the
high voltage transformer. If the operating temperature
of either Magnetron exceeds 302°F (150°C) the thermal
switch opens preventing power to the high voltage
transformer’s primary winding.
If Magnetrons are operating intermittently, check the
thermal switches. The interlock switches should all be
checked as well to ensure they are operating properly.
Magnetron Thermal Switch Replacement
CAUTION:
If the unit has been in operation the
Magnetron housings will be very hot.
Allow the unit to cool before proceeding.
1. Remove the unit from its power source and follow
the proper Lockout/Tagout procedures.
2. Remove the rear service panel. It is also
recommended to remove the top and both side
panels, although this is not necessary if just
replacing a Thermal Switch.
3. Tag and disconnect the Thermal Switch wires.
4. Using an Ohmmeter test the Thermal Switches
for continuity. The switches should be closed at
room temperature. The open at 302°F (150°C). If
one of them is open at room temperature it must
be replaced.
REMEMBER:
The Thermal Switches are connected
in series with the primary winding of the High Voltage
Transformer. Either one will cause the High Voltage
primary circuit to be open.
