• ** REMEMBER! **The microwave can still shock you even unplugged!!

    ALWAYS discharge the high-voltage capacitor first if you even think your hands will come close to any HIGH VOLTAGE components.

    Jeff mentions this: Anything in the high voltage ( magnetron, capacitor, diode, wires to and from ):
    ...Use a metal ( not the shiny chrome type ) screw driver with a insulated handle to short across ( touch both at the same time ) the terminals of the high voltage capacitor to discharge it.

    From Jeff's site: http://www.applianceaid.com/component-testing.php

    Jake

721.81629600 Loud thumping/bumping while cooking

pantherdev

Premium Member
Joined
May 28, 2013
Messages
28
Location
Mineral Bluff, Ga
Model Number
721.81629600
Brand
Sears Kenmore
Age
6-10 years
Depending on food and container, this oven can make minor bumping noise at a rate of 1 per second or a louder bumping noise. I put in a 6" diameter plastic dish with a cup of water and you can barely hear the bumping. Put in baking potatoes and bumping is loud. It definitely has something to do with the duty cycle of mag tube since it stops bumping when you use lower powers during off duty. Anyway; the unit cooks just fine and I am not inclined to go into the unit if noise is the only issue. Should I be concerned about it or let it go? We can live with the noise.
 

rickgburton

Appliance Tech - Moderator
Staff member
Joined
Jul 11, 2006
Messages
35,181
Location
Murray, Utah 84107, United States
Best case scenario, it's just noise or the noise goes away. Worst case scenario the mag tube goes out. If the tube is on it's way out there's nothing you can do to prevent it so just keep using it until it goes. It won't have any effect on other components when it goes out. If the tube goes out it might be better to put that money towards a new machine. The average life for that machine is 5-10 years. You don't want to end up replacing part after part.
 

pantherdev

Premium Member
Joined
May 28, 2013
Messages
28
Location
Mineral Bluff, Ga
Finally got back to you Rick on what is happening with this unit. This unit also cooks conventionally with a heater bar in the top with a chrome steel cage enclosing the heater bar. The cage came loose at one point and that part of the cage was arcing back to the grounded inside of roof. I could not reattach so I just removed the cage and do not use the heater anyway. The bumping became less and less with each use and has disappeared totally with the unit working great. I seriously doubt whether this was the bump noise problem and the two are connected. I do know the blue arc was quite a show when I saw it. So thanks for now and I am working on a Kenmore issue for the moment. I also will not forget the tip jar.
 

rickgburton

Appliance Tech - Moderator
Staff member
Joined
Jul 11, 2006
Messages
35,181
Location
Murray, Utah 84107, United States
I do know the blue arc was quite a show when I saw it.
After I repaired a customers microwave I ask for a cup of water to check it. Didn't know the gold rings around the cup were gold leaf. That was quite a show! Thanks for the update! Glad to hear it's still working!
 
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