TurboChef Technologies Residential Single and Double Wall Oven - Manual (Page 55)

OVEN
SY
STEMS
5.7
Magnetrons
Th e magnetron generates microwave energy by
means of 4000+ volts supplied by the microwave
circuit. Due to the very high voltage present during
operation, the only safe way to test this component
is by a resistance test of its fi lament with the power
disconnected and the capacitors properly discharged.
Th e magnetron can have a good fi lament and still
not operate properly. All of the testing should be
completed on the other microwave components fi rst
before checking the magnetron. If all tests listed
in this manual are completed for the transformer,
diode, and capacitor, and all show to be within
specifi cations, the magnetron will be the defective
component.
CAUTION: Be careful to not allow debris
into the waveguides when servicing the magnetrons.
Stirrer Motor and Assembly
Th e stirrer is responsible for evenly distributing hot
air and microwaves that are launched from the top
of the oven into the cook cavity. Th
e stirrer is driven
by a motor that remains on during a cook cycle.
When the oven is cooling down, the stirrer motor
turns off when the cook cavity temperature recedes
below 160°F (71°C).
To visually test stirrer motor operation, go to Bake,
which will automatically turn on the stirrer, the stir-
rer is visible through the upper jetplate holes.
Waveguides
Th e waveguides channel microwaves into the cook
cavity. To prevent the life of the magnetrons from
being shortened, be careful to not allow debris to
enter into the waveguides when servicing the
magnetrons.
When the high-voltage winding starts to go
toward negative, the high-voltage diode becomes
non-conducting with the charged high voltage
capacitor in series with the high-voltage winding.
When the transformer gets to its negative peak of
-2400, the voltage applied to the fi lament is negative
4000+ volts.
High-Voltage Transformers
Th e high-voltage transformers are ferro-resonant,
limiting fault currents and minimizing magnetron
power changes due to input voltage changes. Th
e
high-voltage transformer supplies the high voltage
for the Voltage Doubler Circuit. For Gen 1 ovens,
they are controlled via the K3 and K4 relays. For
Gen 2 ovens, they are controlled by relays 2 and 3
on the relay board (outputs RBJ5 and RBJ4).
Wiring a High-Voltage Transformer
DANGER: Never attempt to wire or measure
the secondary voltage values of the high-voltage
transformers with the high-voltage transformers
enabled. Lethal voltage will be present.
Th e proper re-installation of a high-voltage
transformer is critical. Upon removing a high-voltage
transformer, make sure to note where each wire was
connected. Refer to the oven schematic (Section 7)
detailing the proper wiring.
As shown in the schematic, transformers are installed
mirror opposite and wired 180° out-of-phase. It is
essential for longevity that the high-voltage
transformers remain 180° out-of-phase. Th
is can
be checked by placing a volt meter across terminals
T1-1 and T2-1 (primary voltage). If the meter reads
0 VAC, the high-voltage transformers are most likely
wired in-phase.
As a last check, energize the microwave system and
verify the voltages between the incoming voltage
taps on each high-voltage transformer. Taps 1 and
2 = 208V. Taps 1 and 3 = 240V. Wiring issues must
be corrected prior to returning the oven to service.
Voltage at the wall must match the transformer
confi guration.