Microwave Oven – How It Works and Repair Tips
Microwave touch buttons do not work. What to do if the microwave oven membrane keypad does not respond to the mode selection on the keyboard. When you press the program selection buttons, nothing happens or the microwave does not respond to all the buttons on the touch panel.
The touch (membrane) keyboard of the microwave oven control unit comes with multilayer film.
It is worth noting that there are many membrane keyboards of different quality, malfunctions and methods of repairing them. Below we will consider the main causes of the malfunction and methods for their elimination.
There are three main reasons for a microwave oven membrane keypad malfunction:
- Break of the conductive tracks of the membrane keyboard.
- Loss of contact at the point of connection between the loop and the connector on the control board. 3. Sticking contacts of the touch panel (membrane keyboard).
- Recovery of damaged tracks
You can determine the breakage of the tracks visually by examining the film for light or by ringing the tracks with a tester. We can restore damaged tracks with the help of special conductive glue. After eliminating the break, in order to avoid a repetition of the defect, it is necessary to protect the tracks from moisture ingress and short circuiting of adjacent tracks.
- Restoration of contact on the connector
It is necessary to check the reliability of the contact of the microwave oven membrane keypad loop in the connector of the control module. If necessary, clean the contacts with alcohol. In some cases, the tracks at the end of the loop destroy. Due to which the contact disappears.
In order to restore contact, the end of the loop must be carefully cut with scissors by a few millimeters and inserted back into the connector.
3. How to fix sticky microwave oven membrane?
Over time, the “touch” buttons of the membrane keyboard presses through and fail. In order for the buttons to be pressed again and not to stick, we need to raise the pressed film of the buttons. We can do it by increasing the distance between the contact planes.
The upper part of the keyboard film must be pry off from the corner with a flat screwdriver and carefully peeled off. In the places between the contacts of the buttons, as an additional layer, we glue strips of adhesive tape. Thereby raising the film and increasing the gap between the film and the contacts themselves.
Microwave ovens often experience such a “creeping” malfunction, as if the oven loses control from the keyboard and begins to “take on a life of its own.” It is the fact that the microwave oven does not respond to keystrokes on the keyboard or spontaneously “starts”.
Moreover, these signs of microwave oven membrane keypad malfunction appear chaotically – randomly. When you turn it on again, the microwave oven can restore to normal operation and work in normal mode for some time.
Consider the causes of the phenomenon and methods of localizing a creeping fault. Practical recommendations on how to make the microwave stop “clowning” are given below.
Reasons for microwave oven membrane keypad malfunction
The reason for the disgrace is that over time (especially in high humidity conditions). The insulation between the keyboard conductors deteriorates. It is impossible to diagnose this malfunction using a millimeter.
Its test voltage is too low. Often (in this case) the repairer decides that the microprocessor in the microwave control unit is fault. In a number of practical cases, it turned out that the best solution is to replace the microwave oven membrane keypad.
Microwave membrane keyboard device
The keyboard consists of two films. Basically we apply; conductive tracks contact pads on it. Between them is a mask, with slots opposite the contact pads. This mask also glues the films.
How to fix a microwave oven membrane keypad?
For repair, you need to glue the keyboard. In this technological process, sharp movements and shaking hands are common. The mechanical force on the upper film comes evenly and not too hard. Then remove the electronic unit.
With a table knife, with a round tip, gently pry off the edge of the films. So that you can grab the top one with your fingers. And then the main thing is not to bend or pull the edges. It is not necessary to glue or tear off the outgoing loop of conductors (it is also not advisable to touch it).
You need to unstick it so that the upper film peels off. And the sticky mask and the lower film remain on the keyboard case. After several attempts (workouts), it usually turns out nice and neat.
But if the repairman is not good at this part of the technological process, he will have nothing to train on. The very first damaged microwave oven will cover the prospect of further repairs. Therefore, you cannot make mistakes, as in demining.
Next, next to the keyboard case, put a book (the book is necessary for the convenience of work) of a suitable thickness (1.5 … 2 cm). We turn open the unsticked. They take a narrow tape (width 6 … 8 mm) and glue the entire surface of the film, except for the contact pads.
Then all the parts return to their places. Moreover, the microwave oven membrane keypad comes in reverse order. Similarly, we install the electronic unit in its regular place, and now we turn on the oven.
Troubleshooting microwave ovens
- Check the grounding before carrying out any work.
- Be careful with the high voltage part of the oven.
- When checking the resistance of the transformer windings or the open-close of the contacts of the switches, disconnect one wire from the circuit under test. In this case, the oven must be disconnected from the mains.
- Do not touch any parts around the control box or the box itself, as static electricity can damage its components. Always discharge static electricity from your body or use an antistatic wrist strap before working on control box circuits.
- Control the operation of the microwave oven with the correct commands (see the instructions for use of the oven).
- If the oven fuse is blown, before changing it. Make sure that the primary, secondary and safety switches are working and working correctly.
Common microwave oven malfunctions:
The microwave oven membrane keypad does not work too many consumers are plugged into the tee of the outlet. It has led to overload. Limit the use of other electrical appliances when turning on the microwave oven.
Low oven power output:
- Low voltage in the supply network. We should not connect oven to a 220 V network.
- The starting temperature of the food being cooked was very low. This is not a defect in the oven. It is possible that food will only cook over a longer period of time.
There are no microwave generation possible reasons:
- Defective output power control relay (relay 2 in U furnaces) of the control unit. We should check it and, if necessary, replaced.
- Defective high voltage transformer, capacitor or diode. Check the indicated elements and replace faulty ones.
- Defective magnetron. The magnetron should be checked and, if necessary, replaced.
- Low supply voltage Use the oven only with a rated supply voltage of 220 V.
- Broken or shorted wires inside the oven. The wiring needs to be repaired. 6. The fuse has blown.