Tech Sheet

FOR SERVICE TECHNICIAN’S USE ONLY
5
Components Test/Results
H.V. Transformer
NOTE: Top wire is orange. Bottom wire is white.
1. Unplug microwave oven or disconnect power.
2. Remove wire leads.
3. Measure resistance:
■ Primary winding: 0.2 to 0.4 ohm (approximate)
■ Secondary winding: 60 to 90 ohms (approximate)
■ Filament winding: Less than 1 ohm
■ Primary winding to grounding: Normal: Innite
■ Filament winding to grounding: Normal: Innite
Magnetron 1. Unplug microwave oven or disconnect power.
2. Remove wire leads. Check that the seal is in good condition.
3. Measure resistance:
■ Filament terminal: Normal: Less than 1 ohm
■ Filament to chassis: Normal: Innite
H.V. Capacitor 1. Unplug microwave oven or disconnect power.
2. Remove wire leads.
3. Prepare the DC 9-volt battery and 10k ohms resistance including wire leads.
4. Connect the DC 9-volt battery to the H.V. capacitor.
5. Measure resistance:
■ Terminal to terminal: Normal: 9 volts (approximate); Abnormal: 0 volts (approximate)
■ Terminal to case: Normal: 0 volts (approximate); Abnormal: 0 volts (approximate)
H.V. Diode
NOTE: Some inexpensive ohmmeters do not have a 9-volt battery incorporated in them, and may indicate
innite resistance in both directions when testing the diode. It is recommended that you use an ohmmeter
with a 9-volt battery on the 10x scale to properly test the H.V. diode.
1. Unplug microwave oven or disconnect power.
2. For ohmmeters without a 9-volt battery, prepare the DC 9-volt battery and 10k ohms resistor in series
including wire leads.
3. Connect the DC 9-volt battery to the H.V. diode.
4. Measure resistance:
■ Forward: Normal: 5 to 6 volts (approximate); Abnormal: Open—9 volts (approximate); Short—0 volts
(approximate)
■ Reverse: Normal: 9 volts (approximate); Abnormal: Open—9 volts (approximate); Short—0 volts
(approximate)
Stirrer Motor 1. Unplug microwave oven or disconnect power.
2. Remove wire leads.
3. Measure resistance:
■ Normal: 3.8k ± 0.2k ohms (approximate)
■ Abnormal: Innite
Cooling Fan Motor 1. Unplug microwave oven or disconnect power.
2. Remove wire leads.
3. Measure resistance:
■ Normal:
A 95 to 120 ohms (approximate)
B 10 to 25 ohms (approximate
■ Abnormal: Innite
5
Microwave Oven Power Output Test
1. Place 8 oz (250 mL) of lukewarm water in the center of the
microwave oven.
2. Operate on HIGH power level for 2 minutes. Water should be
hot.
NOTE: If the water takes longer than 2 minutes to heat, this
may indicate either the operating voltage is lower than
110 volts or there is a problem with the microwave oven.
Component Tests
IMPORTANT:
■ Unplug microwave oven or disconnect power.
■ Discharge the high-voltage capacitor and remove the lead
wires from the primary winding of the high-voltage
transformer before conducting any of the following tests.
■ Remove the lead wires from the related component before
conducting any of the following tests.
■ Conduct a microwave energy test after performing any tests
or repairs to the microwave oven.
■ Check that all wire leads are in the correct positions before
operating the microwave oven.
■ All operational checks using microwave energy must be done
with the microwave oven loaded with a minimum of 8 oz
(250 mL) of water in a microwave safe container.
■ Grasp wire connectors when removing the wire leads from
microwave oven parts.
■ All testing must be done with an ohmmeter having a
sensitivity of 20,000 ohms per volt DC or greater, and
powered by at least a 9-volt battery.
Components Test/Results
H.V. Transformer
NOTE: The inside lead wire is red. The outside lead wire is white. Do not reverse leads.
1. Unplug microwave oven or disconnect power.
2. Remove wire leads.
3. Measure resistance:
■ Primary winding: 0.2 to 0.4 ohm (approximate)
■ Secondary winding: 60 to 90 ohms (approximate)
■ Filament winding: Less than 1 ohm
■ Primary winding to grounding: Normal: Infinite
■ Filament winding to grounding: Normal: Infinite
Magnetron
1. Unplug microwave oven or disconnect power.
2. Remove wire leads. Check that the seal is in good condition.
3. Measure resistance:
■ Filament terminal: Normal: Less than 1 ohm
■ Filament to chassis: Normal: Infinite
5
Microwave Oven Power Output Test
1. Place 8 oz (250 mL) of lukewarm water in the center of the
microwave oven.
2. Operate on HIGH power level for 2 minutes. Water should be
hot.
NOTE: If the water takes longer than 2 minutes to heat, this
may indicate either the operating voltage is lower than
110 volts or there is a problem with the microwave oven.
Component Tests
IMPORTANT:
■ Unplug microwave oven or disconnect power.
■ Discharge the high-voltage capacitor and remove the lead
wires from the primary winding of the high-voltage
transformer before conducting any of the following tests.
■ Remove the lead wires from the related component before
conducting any of the following tests.
■ Conduct a microwave energy test after performing any tests
or repairs to the microwave oven.
■ Check that all wire leads are in the correct positions before
operating the microwave oven.
■ All operational checks using microwave energy must be done
with the microwave oven loaded with a minimum of 8 oz
(250 mL) of water in a microwave safe container.
■ Grasp wire connectors when removing the wire leads from
microwave oven parts.
■ All testing must be done with an ohmmeter having a
sensitivity of 20,000 ohms per volt DC or greater, and
powered by at least a 9-volt battery.
Components Test/Results
H.V. Transformer
NOTE: The inside lead wire is red. The outside lead wire is white. Do not reverse leads.
1. Unplug microwave oven or disconnect power.
2. Remove wire leads.
3. Measure resistance:
■ Primary winding: 0.2 to 0.4 ohm (approximate)
■ Secondary winding: 60 to 90 ohms (approximate)
■ Filament winding: Less than 1 ohm
■ Primary winding to grounding: Normal: Infinite
■ Filament winding to grounding: Normal: Infinite
Magnetron
1. Unplug microwave oven or disconnect power.
2. Remove wire leads. Check that the seal is in good condition.
3. Measure resistance:
■ Filament terminal: Normal: Less than 1 ohm
■ Filament to chassis: Normal: Infinite
6
H.V. Capacitor
1. Unplug microwave oven or disconnect power.
2. Remove wire leads.
3. Prepare the DC 9-volt battery and 10k ohms resistance including wire leads.
4. Connect the DC 9-volt battery to the H.V. capacitor.
5. Measure resistance:
■ Terminal to terminal: Normal: 9 volts (approximate); Abnormal: 0 volts (approximate)
■ Terminal to case: Normal: 0 volts (approximate); Abnormal: 0 volts (approximate)
H.V. Diode
NOTE: Some inexpensive ohmmeters do not have a 9-volt battery incorporated in them, and may
indicate infinite resistance in both directions when testing the diode. It is recommended that you use an
ohmmeter with a 9-volt battery on the 10x scale to properly test the H.V. diode.
1. Unplug microwave oven or disconnect power.
2. For ohmmeters without a 9-volt battery, prepare the DC 9-volt battery and 10k ohms resistor in
series including wire leads.
3. Connect the DC 9-volt battery to the H.V. diode.
4. Measure continuity:
■ Forward: Normal: 5 to 6 volts (approximate); Abnormal: Open—9 volts (approximate); Short—0
volts (approximate)
■ Reverse: Normal: 9 volts (approximate); Abnormal: Open—9 volts (approximate); Short—0 volts
(approximate)
Stirrer Motor
1. Unplug microwave oven or disconnect power.
2. Remove wire leads.
3. Measure resistance:
■ Normal: 3.8k ± 0.2k ohms (approximate)
■ Abnormal: Infinite
Cooling Fan Motor
1. Unplug microwave oven or disconnect power.
2. Remove wire leads.
3. Measure resistance:
■ Normal:
A 95 to 120 ohms (approximate)
B 10 to 25 ohms (approximate
■ Abnormal: Infinite
AC Line Filter
1. Unplug microwave oven or disconnect power.
2. Remove wire leads.
3. Measure resistance:
■ Normal: L(1) to L(2) (coil): Less than 1 ohm;
N(1) to N(2) (coil): Less than 1 ohm
■ Abnormal: Infinite
■ Normal: L(1) or L(2) to N(1) or N(2) (resistor): 1.5M ohms
■ Abnormal: 0 ohms
Components Test/Results
6
H.V. Capacitor
1. Unplug microwave oven or disconnect power.
2. Remove wire leads.
3. Prepare the DC 9-volt battery and 10k ohms resistance including wire leads.
4. Connect the DC 9-volt battery to the H.V. capacitor.
5. Measure resistance:
■ Terminal to terminal: Normal: 9 volts (approximate); Abnormal: 0 volts (approximate)
■ Terminal to case: Normal: 0 volts (approximate); Abnormal: 0 volts (approximate)
H.V. Diode
NOTE: Some inexpensive ohmmeters do not have a 9-volt battery incorporated in them, and may
indicate infinite resistance in both directions when testing the diode. It is recommended that you use an
ohmmeter with a 9-volt battery on the 10x scale to properly test the H.V. diode.
1. Unplug microwave oven or disconnect power.
2. For ohmmeters without a 9-volt battery, prepare the DC 9-volt battery and 10k ohms resistor in
series including wire leads.
3. Connect the DC 9-volt battery to the H.V. diode.
4. Measure continuity:
■ Forward: Normal: 5 to 6 volts (approximate); Abnormal: Open—9 volts (approximate); Short—0
volts (approximate)
■ Reverse: Normal: 9 volts (approximate); Abnormal: Open—9 volts (approximate); Short—0 volts
(approximate)
Stirrer Motor
1. Unplug microwave oven or disconnect power.
2. Remove wire leads.
3. Measure resistance:
■ Normal: 3.8k ± 0.2k ohms (approximate)
■ Abnormal: Infinite
Cooling Fan Motor
1. Unplug microwave oven or disconnect power.
2. Remove wire leads.
3. Measure resistance:
■ Normal:
A 95 to 120 ohms (approximate)
B 10 to 25 ohms (approximate
■ Abnormal: Infinite
AC Line Filter
1. Unplug microwave oven or disconnect power.
2. Remove wire leads.
3. Measure resistance:
■ Normal: L(1) to L(2) (coil): Less than 1 ohm;
N(1) to N(2) (coil): Less than 1 ohm
■ Abnormal: Infinite
■ Normal: L(1) or L(2) to N(1) or N(2) (resistor): 1.5M ohms
■ Abnormal: 0 ohms
Components Test/Results
6
H.V. Capacitor
1. Unplug microwave oven or disconnect power.
2. Remove wire leads.
3. Prepare the DC 9-volt battery and 10k ohms resistance including wire leads.
4. Connect the DC 9-volt battery to the H.V. capacitor.
5. Measure resistance:
■ Terminal to terminal: Normal: 9 volts (approximate); Abnormal: 0 volts (approximate)
■ Terminal to case: Normal: 0 volts (approximate); Abnormal: 0 volts (approximate)
H.V. Diode
NOTE: Some inexpensive ohmmeters do not have a 9-volt battery incorporated in them, and may
indicate infinite resistance in both directions when testing the diode. It is recommended that you use an
ohmmeter with a 9-volt battery on the 10x scale to properly test the H.V. diode.
1. Unplug microwave oven or disconnect power.
2. For ohmmeters without a 9-volt battery, prepare the DC 9-volt battery and 10k ohms resistor in
series including wire leads.
3. Connect the DC 9-volt battery to the H.V. diode.
4. Measure continuity:
■ Forward: Normal: 5 to 6 volts (approximate); Abnormal: Open—9 volts (approximate); Short—0
volts (approximate)
■ Reverse: Normal: 9 volts (approximate); Abnormal: Open—9 volts (approximate); Short—0 volts
(approximate)
Stirrer Motor
1. Unplug microwave oven or disconnect power.
2. Remove wire leads.
3. Measure resistance:
■ Normal: 3.8k ± 0.2k ohms (approximate)
■ Abnormal: Infinite
Cooling Fan Motor
1. Unplug microwave oven or disconnect power.
2. Remove wire leads.
3. Measure resistance:
■ Normal:
A 95 to 120 ohms (approximate)
B 10 to 25 ohms (approximate
■ Abnormal: Infinite
AC Line Filter
1. Unplug microwave oven or disconnect power.
2. Remove wire leads.
3. Measure resistance:
■ Normal: L(1) to L(2) (coil): Less than 1 ohm;
N(1) to N(2) (coil): Less than 1 ohm
■ Abnormal: Infinite
■ Normal: L(1) or L(2) to N(1) or N(2) (resistor): 1.5M ohms
■ Abnormal: 0 ohms
Components Test/Results