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ISSUE RESOLUTION
F3 Fuse Blown, cont. c. Monitor circuit fault: Verify operation of all interlock switches.
In addition, check the Fault Log. If the monitor switch opened prior to
the primary and secondary, the control would have recorded the
occurrence. See page 25 as well as Chapter 6 (Oven Door) for
troubleshooting (see
F4 MONITOR).
Mag 1 or Mag 2 Not
Working or Food Not
Cooking Evenly
Determine which magnetron is not oscillating by placing a clamp-on
amp meter on the primary winding of each high-voltage transformer
and energizing the Microwave System.
1. Amp = 0. High-voltage transformer not energizing.
Check K2 relay and wiring going to suspect high-voltage transformer.
K2 relay or wiring bad: Replace K2 relay and/or repair wiring.
K2 relay OK: Check high-voltage transformer. See the table on page
33 for resistance values. Unplug the oven and replace high-voltage
transformer if defective.
2. Amps = 3 amps on high-voltage transformer. Magnetron is not
oscillating, but high-voltage transformer is energizing.
Diodes failed: Unplug the oven and replace the diodes.
Diodes OK: Unplug the oven and replace the defective magnetron.
Magnetron Circuit
is Drawing Excessive
Current.
Measure resistance of high-voltage capacitor(s).
Resistance should start out in the megohm range and continue to rise as
the probes are held on the capacitor. If the resistance is low (less than the
megohm range), unplug the oven and replace the capacitor. Visually check
the associated high-voltage transformer primary winding for signs of over-
heating (winding is very dark and discolored). If transformer primary
winding looks bad, replace it.
High Voltage and/or
Filament Transformer(s)
Faulty
Determine if the high-voltage or filament transformer(s) is defective.
Use an ohm meter to measure the primary and secondary winding
resistances. Refer to the high-voltage and filament transformer table on
page 33 to determine if the transformer is OK. If the resistance is
different then the table indicates, ensure the oven is unplugged and
replace the transformer.
Wave Guide
Covers Broken
Replace the wave guide covers. Follow the instructions on pages 29-30 and
Figure 22 on page 29. Inspect the wave guides for debris. If debris is pres-
ent, replace the wave guide and the magnetron.
THE MICROWAVE SYSTEM
36