My wifi router in my bedroom does not have auto ON/OFF function. I don't like to have strong wifi signal in my bedroom all the time. So, I have a digital timer to switch on and off the power in a scheduled way (ON at 6 am and OFF at 1 am).
More important, it can control myself so that I won't work after 1 am. :P
The timer works perfectly for a year but it was broken with no reason... Very embarrassed that I forgot everything about electronics I learned from school...
It seemed no hope to get it working again. Thanks Google again. I found someone had the same problem and he fixed it successfully.
I only needed to buy a FOUR-dollar capacitor (yellow one in the pic) and replace the broken one.
And it is now working perfectly again. Thanks Google, and the master who posted his solution in the web forum.