Service manual

29
!
WARNING
To avoid risk of electrical shock, personal injury or death; disconnect power to oven and discharge capacitor
before servicing, unless testing requires power.
Illustration Component Test Results
Thermal cutout Disconnect all wires from TCO.
Measure resistance across terminals.
Control TCO .............................................
Magnetron TCO .......................................
Closed at 235°F (113°C) and open at
150°F (66°C)
Open at 300°F (149°C) and closed at
257°F (125°C)
Diode
Discharge Capacitor
Remove diode lead from capacitor and
connect ohmmeter.
Reverse leads for second test.
Infinite resistance should be measured
in one direction and 50KΩ or more in
the opposite direction.
NOTE: Ohmmeter must contain a
battery of 6 volts minimum.
MT2
MT1 GATE
Triac Disconnect wires to triac.
Measure resistance from:
MT1 to MT2..............................................
MT1 to Gate .............................................
MT2 to Gate .............................................
All terminals to ground .............................
Caution - Do not operate oven with
wire to terminal MT2 removed.
Infinite
Approximately 15 Ω, then reverse
meter leads 30 Ω
Infinite
Infinite
Triac 1 (top) is for front element
Triac 2 (middle) is for rear element
Measure voltage from:
MT1 to Gate
0.8 VAC when energized. If no
voltage, check H.V. board and wiring.
Capacitor
Discharge Capacitor
Remove wires from capacitor terminals and
connect ohmmeter, set on highest
resistance scale to terminals.
Also check between each terminal and
capacitor case..............................................
Between Terminals: Meter should
momentarily deflect towards zero then
return to over 5 MΩ. If no deflection
occurs, or if continuous deflection
occurs, replace capacitor.
Terminal to Case: Infinite resistance
Snubber assembly Disconnect wires to snubber.
Measure resistance across terminals.......... Infinite
Magnetron
Discharge Capacitor
Remove wires from magnetron and
connect ohmmeter to terminals. Also check
between each terminal and ground.
Between Terminals: Less than 1 Ω
Each terminal to ground measures
Infinite resistance.
Note: This test is not conclusive. If
oven does not heat and all other
components test good replace the
magnetron and retest.
Cooling blower
motor
Measure voltage at motor
Approximately 24 vdc at incoming leads
Stirrer motor Remove all wires from terminals.
Measure resistance from:
Terminal to terminal.....................................
Approximately 29K Ω
Line filter
Remove all wires from terminals.
Measure resistance from:
Red to Brown wire.....................................
Ω
Infinite
Blue to Blue wire .....................................
Infinite
Ω
Cavity TCO .............................................
Open at 262°F (128°C)
Thermal cutout
Component Testing Procedures