Tutorial on LG Intellowave Microwave Oven MG-396WA / MG-397WB, Touch-Pad Control Panel (part no. 6871W1S090B PCB Assembly) Replacement.
Control panel of Microwave Oven consists of two components, touch-pad membrane switch and the PCB control board.
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Most Frequent Causes for Microwave oven buttons not working:
· If the touch-pad is defective, try pressing each of the buttons on the control panel. If some of the buttons respond correctly while others don’t, replace the touch-pad.
· If the control and display board is defective, try pressing each of the buttons on the control panel. If none of the buttons is responding correctly, replace the user control and display board.
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| Control and Display Board |
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| Touch-Pad membrane switches |
The membrane switch is usually made up of two layers of a thin Mylar plastic with a conductive material on the inner surface. Two surfaces will separate the conductive coatings by a formed gap. Signal will not generate until pressure is applied by the user. When the two conductive surfaces come in contact with each other, an electrical circuit is completed to provide an input signal to the control board. With repeated use, the conductive coating will eventually wear out and be unable to make a good enough contact to send the signal to the control board.
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The control circuit generates a low voltage which sends to the membrane switch. The voltage signal is switched back to the control circuit after taping each function switch on touch-pad panel. The control circuit uses these input signals/commands to turn on output relays that control the various components of the oven such as turntable motor and magnetron which generates microwave radiation.
