After the microwave oven is opened, it is found that the structure of the electronic key is the same as the mechanical structure of the mechanical knob. After the understanding, the computer board is removed, leaving only the power control board, and the power control board directly on the timing switch, cover the shell, in the microwave oven put a bottle of pure water. Plug in the power, the microwave oven immediately start up, the lights, the turntable rotation... (everything is normal microwave oven sound, a few seconds after unplug the power, open the door out of pure water has been warm). This indicates that the failure of the microwave oven is still on the computer board and connected with the computer board.

The computer board brought a careful study, its working principle is: connection cn7 through conductive rubber to the liquid crystal display display working state of microwave oven; CN8 connected by conductive rubber to film button, keyboard keys to receive instructions; connecting cn6 is connected to the power control panel by means of a flat cable, from the power control panel access computer board power supply; but at the same time, the keyboard commands through the CPU processing, output to the power supply on the control board to drive the relay, to control the operation of the microwave oven.

Take the microwave oven panel and remove the film from the front panel. The thin film keyboard is glued on the front panel. Then leave the keyboard and then printed circuit film film removed.

According to the definition of each key on the panel and printed film circuit, the CN8 each foot is a combination of short answer, see table.

The computer board is installed (the panel is not installed). After the safety protection measures, the short wiring short CN8 the command line. Microwave oven works display normal. So it is decided that the problem is on the membrane keyboard.

All the key points of the printed film circuit are measured by using the meter to measure the contact points. Gradually narrow the measurement range, and finally determine the point in the vicinity of the printed film circuit and conductive rubber contacts (bending) place. A conductive silver paste, which is bought in a half month ago, to repair a laptop keyboard, is carefully applied to the printed circuit breakpoint. Put in a few hours to dry, with the use of the table once again to measure the key points and conductive rubber joints have been. When the keyboard, the panel mounted back to power, microwave oven to resume normal work. So far, repair work done.