Question about KitchenAid KHMS2050SSS Microwave Oven
Found and replaced bad monitor door switch. still nothing. Get a buzz every 2 seconds or so as if the magnetron is trying to engage; but then it kicks out. Any ideas? Haven't checked mag yet but i'm suspecting it. Found 0 Ohms on the mag. No shorts to housing. Will replace and hope there are no other problems. Checked another magnetron. Got 0 ohms as well. Got a known good invertor to try. Same problem. Just get a slight faint buzz for a split second every two seconds as if is trying to start but doesn't. Without any schematics or manuals it is going to get difficult.
The magnetron is supposed to read nearly zero ohms across the two terminals. You are measuring the resistance of the filiament/heater/cathode of the tube. Activity in the magnetron occurs when the heated electrons are emitted from the cathode, pass through the magnetic field, swirl about, bounce in and out of indentations (vanes) in the tube, and finally land on the plate (antenna). The resistance from the cathode to the plate should be infinite. If not, you probably have a bad tube. Or, if there is continuity between the heater and the case, then you have a shorted tube.
What eventually happens to most vacuum tubes is that the cathode (filiament in this case) becomes coated with a material which inhibits the launching of electrons into the tube. When the flow becomes too low, oscillation ceases, and you have no microwave output. Sometimes they reach the threshold, but do no cross over quickly. Then you have a magnetron that is intermittent for a while.
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Posted on May 19, 2016
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Posted on Jan 02, 2017
From a similar model's tech sheet (and yours should have one hidden inside):
Power to magnetron interrupted
1. Unplug microwave oven or disconnect power.
2. After 40 seconds, check to see whether this solves the problem.
3. Check resistance of the magnetron thermostat.
4. Check the magnetron. See this file for details.
5. Check wiring to the 1100W inverter and control system. See "Checking Inverters"
6. Check operation of all interlock switches. See this text file. Check door, hinge and cavity front alignment. Adjust as needed.
7. If switches operate correctly, replace 1100W inverter.
8. If problem persists, replace electronic control.
9. Plug in microwave oven or reconnect power.
You can find helpful exploded view diagrams and order parts by entering your full model number (KHHS179LSS2 without dashes or spaces) from the tag on the oven here.
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Posted on Nov 27, 2010
Perhaps the "repairman" should take another look at it. A lot of microwave ovens have an aerial that directs the energy out to the load or food to be heated.
Maybe...maybe not but worth a look behind the waveguide cover I would say.
Posted on Mar 24, 2011
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