Service Manual for
RCO Speed Oven
24
rear of the unit behind the Magnetron Blower Assembly.
High Voltage
Transformers
Location of HV Transformers
Operational Testing
The right and left Mag circuits use identical components
and wiring. Each Mag circuit has a dedicated 2.4KV
secondary supply from the Mag transformer and a high
voltage doubling circuit (capacitor and diode package)
to step up to the 4KV microwave power.
The primaries of the Mag transformers have 208V or
240V taps auto-selected by the controller PCB, based
on sensed line supply voltage to the oven through the
Tap Relay, to automatically optimize microwave power
at either the 208V or 240V line supply to the unit.
Operations of both right and left Mag circuits are
controlled through a single SSR (Solid State Relay).
The controller PCB, Primary Interlock Switch, and
Secondary Interlock Switch circuits interact to enable
or trigger the Mag SSR only when the oven door is
closed and a microwave recipe is selected.
The Monitor circuit detects failures in the Mag circuits from
the output of the Mag SSR to the Monitor Door Switch
to the Monitor Relay coil. The Monitor circuit disables
the oven by tripping the internal 30A Fast Blow Fuse
if Mag power is detected with the oven’s door open or
ajar through the output contacts of the Monitor Relay.
L1
+
MAG
T1
–
L1
30A†Fuse
208
240
NC
NO
2
NC
NO
1
230V~ COIL
Secondary
Interlock Sw.
Left
Primary
Interlock Sw.
Monitor
Relay
Tap Relay
NO = 208,††NC = 240
Bottom Right
Monitor
Sw.
Top Right
NO
NC
NO
NC
NC
NO
MAG. XFMR –
PRIMARY
MAG. XFMR –
PRIMARY
208
240
NC
NO
2
NC
NO
1
24Vdc COIL
L2
L2
L2
L2
Controller
PCB
Magnetron Control Schematic
High Voltage Diode
(HV016 HV015)
Chassis GND wire to
Xfmr mounting plate at
earth / safety / chassis GND
Chassis GND
via waveguide
weldment
Chassis GND Xfmr winding
to the Xfmr stack to the
Xfmr mounting plate to
earth / safety / chassis GND
0.85F
2500V
Magnetron
F
FA
6B
6A
2K
C1
+
6V
SECONDARY
2.4 kV
SECONDARY
Magnetron Circuit Schematic
HV Transformer Replacement
1. Remove the unit from its power source and follow
the proper Lockout/Tagout procedures.
2. Remove the top and rear service panels.
3. Discharge the High Voltage Capacitors, refer to
the Discharging the High Voltage System section
of this manual.
4. Remove the Magnetron Blower Assembly; refer to
the Magnetron Fan Motor Replacement section of
this manual.
5. Tag and disconnect the Magnetron and Magnetron
Thermal Switch wiring.
