Turbo Chef Technologies Understanding F3 Magnetron Current and Turbochef Filament Transformers in the i5 Oven

Microwave System

The i5 oven employs two independent microwave systems (left and right). In the case of an over- current situation relative to the left system, the F3 fuse will blow. In the case of an over-current situation relative to the right system, the F4 fuse will blow.

This section contains information about the following components:

-Capacitors

-Filament Transformers

-High-Voltage Diodes

-High-Voltage Transformers

-Magnetrons

-Stirrer Motor and Assembly

-Wave Guides

This section also contains procedures for:

-Testing a capacitor

-Wiring the filament transformers

-Testing a filament transformer

-Testing a high-voltage diode

-Wiring the high-voltage transformers

-Testing a high-voltage transformer

-Testing a magnetron for an open/shorted filament

For information on accessing and removing parts, see the Appendix.

Capacitors

-Capacitor rating is 0.91uF, 2500 VDC for all 60 Hz installations (except Japan).

-Capacitor rating is 1.15uF, 2500 VDC for all 50 Hz installations.

-Capacitor rating is 0.85uF, 2500 VDC for 60 Hz Japan installations.

Testing a Capacitor

DANGER: Never attempt any measurement of the capacitors while they

are enabled. Lethal voltage will be present. Measure only in compliance with these procedures.

1.Disconnect the oven from the power source.

2.Fully discharge the capacitor.

3.Isolate the capacitor from the circuit.

4.Check for an open or shorted capacitor by placing ohmmeter leads between the capacitor terminals:

-Inconsistent readings = capacitor OK

-Constant infinite resistance = capacitor open

-Constant very low resistance = capacitor shorted

5.If the capacitor is not open or shorted, set the meter to measure capacitance and again place the leads between the capacitor terminals. The meter reading should equal the label value, plus or minus 10%. If not, replace the capacitor.

Filament Transformers

For better operation and reliability, the oven uses separate transformers in order to preheat the magnetron filament.

The control energizes the filament transformers for approximately five seconds prior to energizing the Microwave Circuit via the high-voltage transformers. When in operation, the filament transformers supply approximately 3.15 VAC at 10 amps to each magnetron filament. The filament transformers are controlled via the K1 relay.

Wiring the Filament Transformers

DANGER: Never attempt to measure the secondary voltage values of the filament

transformers when they are enabled. Lethal voltage will be present.

The installation of filament transformers is straightforward. Filament transformers are wired in-phase and in-line. Refer to the schematic on page 51, detailing the proper wiring.

To verify correct wiring (North America), measure the voltages between terminals 1 & 2 and 1 & 3 on FT1 and FT2. The voltages must be 208 and 240 VAC respectively.

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OVEN SYSTEMS