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Worse than I feared.

A project log for Microwave oven keypad repair

My trusty KIC microwave oven is no longer functioning, because of a keypad failure. I think it's repairable.

Niel MalanNiel Malan 11/29/2018 at 08:072 Comments

I though that the problem might be simply that some deposition had formed between an incoming and outgoing conductor, causing a short circuit or a leak. In that case all that might be needed would be a simple cleaning. 

I don't think it's going to be that simple. As far as I can tell all the traces are printed on, which means, I think, that it is the interleaved layer of insulation that is failing. 

Discussions

Niel Malan wrote 11/29/2018 at 19:13 point

Yes, I have disconnected the keypad from the control circuitry. This was my first indication that it was the keypad that was the problem: on power-on the screen does not give its usual test pattern, but acts like a button was pressed. If the keypad is unplugged, the normal test pattern appears.

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Mike Szczys wrote 11/29/2018 at 16:03 point

Have you disconnected the keypad from the control circuitry? If not, this sounds to me more like a problem with the IC that is scanning the key matrix (an internal short). If you can disconnect the keypad, then check continuity, you can establish if it's actually a circuit board problem or a chip problem.

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