Saturday, December 03, 2016

How to test a Microwave oven Magnetron

Magnetron Test for Opens, shorts or Insufficient Power
Unplug the unit
Discharge all the H.V Capacitors.
Disconnect all the leads (connectors) from the magnetron terminals.
Step 1
Using an Ohm meter on its lowest resistance scale, measure the
resistance from one magnetron terminal to the other in either direction as shown on the illustration.
Meter should read less than 1Ω indicating that the filament is good. If Filament checks good, proceed to Step 2
Step 2
Using an Ohm meter on its highest resistance scale, measure the resistance from one of the magnetron terminals to the metal casing of the magnetron as shown on the illustration on the left.
Meter should read infinity (open circuit) regardless of meter polarity.
If the meter indicates a short (Less than 1 ), the magnetron is defective.
The following temperature test will indicate if a magnetron is weak. Make sure unit is plugged in.
1. Fill a beaker or cup with EXACTLY 8 oz (1 Cup) tap water.
2. Record the temperature of the water (Should be approx. 70o F)
3. Place it in the center of the microwave and heat it for the time specified*.
4. Water should be boiling. Record the temperature again.
5. Temperature should rise approximately 142o F (Go to Step 6 only if temperature rise is considerably lower than 142o F otherwise all magnetrons are functioning properly)
6. To test for the weak magnetron, connect one magnetron at a time and repeat Steps 1-4.
a. For ovens that contain 2 magnetrons (NE1257R, NE1258R, NE1757R, NE2157R), the temperature rise should be approximately 70o F per magnetron.
b.For ovens that contain 4 magnetrons (NE2180, NE3280), the temperature rise should be approximately 35o F per magnetron.
Field Expedient Power Determination Tests:
All times calculated using water starting at 70°F {21°C} brought to 212°F {100°C}.
Times given below should serve as the benchmark. 
MODEL
AMOUNT OF
WATER:
VESSEL:
TIME:
NE-1257/8
1 CUP
PYREX MEASURE
2:15
NE-1757
1 CUP
PYREX MEASURE
1:35
NE-2157
1 CUP
PYREX MEASURE
0:54
NE-2180
1 CUP
PYREX MEASURE
0:54
NE-3280
1 CUP
PYREX MEASURE
0:40