One of my teachers has a Scrabble set that she purchased at a garage sale. It's a 50th Anniversary Edition which came with fancier pieces and board, a dictionary, and a timer. The timer did not work. I tried to help by replacing the single AAA battery, but that didn't fix it.
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| Scrabble timer (photo from eBay) |
The old AAA battery was very corroded, especially at the negative end (because it expired 18 years ago!). The negative terminal in the battery compartment was also extremely corroded. I took the timer home for further troubleshooting. Once I opened the timer, I could see that the negative wire inside was corroded off, and the PCB was damaged around the button.
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| timer battery and spring terminal (stretched during removal) |
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| Negative end of the timer battery |
My mom's digital kitchen scale had the same problem with the wire corroding off, and I was able to fix it by just replacing the wire. For the timer repair, I had to replace both the negative wire and terminal spring, using parts I salvaged from other things I took apart.
The corrosion on the timer continued onto the circuit board. First, I tested to see if the chip was still functional by connecting a AA battery to the solder joints on the circuit board. I heard a beep, which meant the chip was getting power, so I decided to continue the repair attempt. I cleaned the switch area with alcohol, but the damage was too severe. It's the worst corrosion I've ever seen.
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| Example of a corroded circuit board- photo by Brabus on eevblog.com |
The screen display worked, but the button did not. So next, I cleaned around the pcb button area. It still didn't work. I replaced the rubber dome part of the button with conductive foam shielding from a satellite dish. Then it worked, although the feel of the button was different. I discovered that it is a 3 minute timer- perfect for timing ramen noodles. 😋
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| Conductive foam |
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| Conductive foam |
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