I have a panasonic convection/microwave. Last night, after I cleaned it, using oven cleaner on a sponge, it made a loud humming noise after running on microwave for about 10 sec. It does not make the noise when using the convection oven. I don't know if any heating occurred during the brief time before the humming started. Is there something that got wet and needs to dry out, or needs cleaning? What might be wrong? Should I try using it again, or would that make the problem worse?

Almost any non-abrasive cleaner would be okay. Use something that can cut grease and I would also recommend using a sponge or wash cloth and nothing abrasive so that you do not scratch any of the paint.

The magnetron is faulty causing the loud noise.

A loud humming noise in microwave mode will usually be a shorted high voltage diode or bad magnetron.

Hi,

Here is a tip that will help you to figure out what is wrong with your Microwave Oven....

Microwave Oven Basic Troubleshooting Tips

heatman101

A dirty or damaged wave guide cover can cause sparks, fire and noises. You can order a replacement wave guide cover from many appliance parts websites for less than $15 in many cases. It should fix the problem.

In all likelihood the mangnetron has failed, or perhaps even the Power Supply. You need to have it serviced by a reputable service centre/man. Ensure you get a firm "Quote" before proceeding, and remember these days the cost of repair can equal or exceed the price of a new one.

I've found the best way to get grease to loosen up in any oven is to place a glass or coffee cup of undiluted ammonia in the oven overnight. The ammonia vapors attack the grease, softening it. The next day:

1. remove the ammonia
2. mix it with a 2 cups of water
3. wear protective gloves
4. using a non-abrasive cloth or sponge wipe the grease off the surfaces.
5. switch to clean water only, wipe the oven one last time to remove the ammonia residue left by the cleaning.

All:
I have a 2003 Sears Ultra Wave microwave 721.63682300 with a similar problem. A few months ago it started giving off short buzzes when turned on. That stopped but then I noticed that everything took twice as long to heat up. After quite a bit of teardown&inspection I found a circuit break in the inverter board leading to ZD704 diode (pictured). I will now try to find a replacement diode to see if replacing will fix it. Thanks for your postings.

From GEAppliances.com: Microwave - Cleaning Recommendations To minimize the possibility of electric shock, unplug the microwave from the power supply before attempting any maintenance or cleaning. Spills and spatters clean up easily with a damp, soapy paper towel or sponge. It is best to clean soil as soon as it appears. Baking soda and water may also be used. If the food has cooked onto the interior, heat one cup of water on full power for three minutes. The heat and steam help to soften the food. After the three minutes, allow five additional minutes stand time then clean as usual. A non-abrasive scrubbing pad cleaner works well for stubborn stains. You may use mild dish washing liquid or cleaners specifically listed for cleaning interiors of microwave ovens such as MicroBryte® (wx10x3030) or Microwave Oven Magic®. We do not recommend using other detergent based cleaners because they can cause the plastic parts to crack. You may purchase microwave interior cleaner by calling our parts department at 1-800-626-2002, on-line from GE Parts or from your local grocer. For stainless steel interiors of microwave/convection models, we recommend a plastic, soap-filled scouring pad. Rubbing gently with this pad will help remove soil. For the door surfaces (both interior and exterior) We recommend you use only mild, non-abrasive soaps, or detergents applied with a sponge, or soft cloth. For the control panel Wipe with a soft, damp cloth. Dry immediately with a soft cloth. Do not spray any solution directly onto the controls Important: Commercial Oven Cleaners, abrasive cleaners, or cleaners containing ammonia or bleach (can make the plastic brittle) should not be used on any part of the microwave. -- From me - Maybe local restaurants in your area would have some tips? Otherwise, try a Google search for keywords: cleaning stainless steel oven

We had this problem with a new GE microwave in our last home. GE service replaced fan assy,.AND added rubber foam around the motor, Loud hum was reduced,but never did completely go away. We learned to live with it/