I was asked to repair a Sharp EL-240SAB Electronic Pocket Calculator that was not working properly. It had been dropped and the LCD would not display the digits properly. All of the calculations looked like they were fine but the display was faded.
The cost of this calculator is $4 but the fix was quick and easy.
Using a small Phillips screwdriver from my dollar store set I unscrewed the 6 screws on the back.
The calculator had a PCB that was connected to the LCD by a thin ribbon cable. I would hesitate to call this a cable. It was more of a thin plastic film with a carbon coating for traces. This cable had pealed from the PCB.
Soldering this back to the PCB would be impossible. I was sure that the minute I touched the ribbon cable with a soldering iron it would burn. The ribbon could be replaced with a more durable one but that would be a lot of work. I would have to find a ribbon cable thin enough to allow me to close the back case. I would also have to remove the tape from the back of the LCD panel and add new solder traces.
So I took the easy solution. I taped the ribbon cable back to the PCB using scotch tape. I used five pieces of tape and cross layered them so it should last a while. Ideally you should use Kapton tape. Kapton tape would last longer and is ESD safe. But, lacking Kapton tape, scotch tape had to suffice.
Saturday, May 31, 2008 | DIY, Saving | 0 comments »