Repairing chipped digital LCD screens: This is usually the cause 

If even one part of a digital LCD is chipped, you think, "It's broken!" Many people probably don't hesitate to buy a new timer from a 100-yen shop. However, if you understand the display principle, it's easy to repair, so if you don't mind putting in a little effort, you can avoid spending money.
*Some content corrections (pointed out by viewers)
4:30 KURE5-56 and S.T. WD-40 contain solid matter, so it is better not to use them on electrical contacts. Also, some people don't use contact cleaners because they contain adhesive ingredients.
There is a section on removing verdigris in the video, but if you're interested, you can watch it here.
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