39
OVEN SYSTEMS
Testing a High-Voltage Diode
DANGER: Never attempt to measure high
voltage directly. Death or serious injury
could result.
1. Disconnect the oven from the power source.
2. Fully discharge the capacitors.
3. Connect the voltage meter in series with high-
voltage diode.
4. Using a multimeter set to DC voltage, connect
one meter lead to one side of a 9-volt battery and
the other lead to one side of the high-voltage diode.
5. Connect the other side of the 9-volt battery to the
other side of the high-voltage diode. DC voltage
should be present on the meter in only one direction.
6. Switch the meter leads on the high-voltage diode,
which will cause the opposite reading to be
visible. Depending on the voltage of the battery,
voltage between 5-7 VDC should be present in
only one direction and 0-0.1 VDC in the other
direction.
Magnetrons
Magnetrons supply the RF energy at 2.45 GHz
and begin to oscillate when they are supplied with
approximately 4.1 kVDC at approximately .350 mA.
During operation, each magnetron will output a
nominal 1 kW of power.
Perform a microwave leakage test (page 36) after
installing a new magnetron or reinstalling an old one.
CAUTION: Do not allow debris to enter
the waveguides when servicing the magnetrons.
Magnetron Cooling Fans
The magnetron cooling fans (outer fans on the
back panel) are actuated by the K7 relay when the
magnetrons are in operation, and remain on for four
minutes and fifteen seconds after the magnetrons turn
off. They operate at:
- 208/240 VAC (60 Hz with voltage sensing)
- 220 VAC (60 Hz with no voltage sensing)
- 230 VAC (50 Hz installations)
NOTE: The magnetron cooling fans are actuated by
the K7 relay when the EC temperature exceeds 120°F
(49°C), regardless of magnetron operation.
High Voltage Transformers Primary Voltage, Frequency, Taps,
and Resistance
Secondary Taps and Resistance
NGC-3062-1 208 VAC, 60 Hz, 1 & 2,
0.819–1.001 Ω
240 VAC, 60 Hz, 1 & 3,
0.972–1.188 Ω
4, Ground, 53.60–65.52 Ω
NGC-3062-2 230 VAC, 50 Hz, 1 & 2,
0.972–1.188 Ω
3, Ground, 57.52–70.30 Ω
Filament Transformers Primary Voltage, Frequency, Taps,
and Resistance
Secondary Taps and Resistance
NGC-3061-1 208 VAC, 60 Hz, 1 & 2,
17.49–21.37 Ω
240 VAC, 60 Hz, 1 & 3,
20.61–25.19 Ω
4, 5, very low resistance - if reading
is open, transformer has failed.
NGC-3061-2 230 VAC, 50 Hz, 1 & 2,
18.99–23.21 Ω
4, 5, very low resistance - if reading
is open, transformer has failed.
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