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THE MICROWAVE SYSTEM
33
HIGH VOLTAGE TRANSFORMERS PRIMARY VOLTAGE, FREQ, TAPS,
AND RESISTANCE
SECONDARY TAPS AND
RESISTANCE
NGC-3062-1 208 VAC, 60 Hz, 1 & 2,
0.819–1.001
W
240 VAC, 60 Hz, 1 & 3,
0.972–1.188
W
4, Ground, 53.60–65.52
W
NGC-3062-2 230 VAC, 50 Hz, 1 & 2,
0.972–1.188
W
3, Ground, 57.52–70.30
W
NGC-3062-3 200 VAC, 50/60 Hz, 1 & 2,
0.784–0.958
W
3, Ground, 55.75–68.13
W
FILAMENT TRANSFORMERS PRIMARY VOLTAGE, FREQ, TAPS,
AND RESISTANCE
SECONDARY TAPS AND
RESISTANCE
NGC-3061-1 208 VAC, 60 Hz, 1 & 2,
17.49–21.37
W
240 VAC, 60 Hz, 1 & 3,
20.61–25.19
W
4, 5, very low resistance - if read-
ing is open, transformer has failed.
NGC-3061-2 230 VAC, 50 Hz, 1 & 2,
18.99–23.21
W
3, 4, very low resistance - if read-
ing is open, transformer has failed.
NGC-3061-3 200 VAC, 50/60 Hz, 1 & 2,
15.70–19.18
W
3, 4, very low resistance - if read-
ing is open, transformer has failed.
HIGH VOLTAGE AND FILAMENT TRANSFORMER RESISTANCE TABLE
How to Check a Capacitor
1. Disconnect the oven from the power source.
2. Fully discharge the capacitor.
3. Isolate the capacitor from the circuit.
4. Connect the ohmmeter between the capacitor
terminals. The ohmmeter should momentarily
indicate a low impedance and then slowly return
to infinite resistance.
5. Reverse the ohmmeter leads and repeat Step 4.
6. Check each terminal to case. Infinite resistance
(open) should be indicated.
How to Check a Magnetron for Open/Shorted Filament
1. Disconnect the AC power source and discharge
the high-voltage capacitors.
2. Isolate the magnetron from the circuit by removing
the wires from the F and FA terminals. Figure 25.
3. An ohmmeter connected between the filament
terminals (F, FA) should indicate a reading of
less than 1 ohm. Figure 25.
4. A continuity check between either filament
terminal and the magnetron chassis should indi-
cate an infinite resistance (open).
How to Check a High-Voltage or Filament Transformer
1. Disconnect the AC power source and discharge
the high-voltage capacitors.
2. Disconnect all the wires in question going to
the transformer.
3. Use an ohmmeter to check the impedance of the
primary and secondary winding. Refer to the
high-voltage and filament transformer table below
to determine if the transformer is OK. If the
resistance is different then the table indicates,
replace the transformer.