Repairing power extension plug

[goall]

Over the years, I have managed to accumulate quite many non-working power extension plugs. The plugs stop working for no apparent reason.
Needless to say, this situation bothers me a lot as it showcases how much money I have lost in purchasing these power accessories. I'd naturally want to recoup my money by repairing the plugs.

Can you share on whether it is possible to repair these accessories?
Perhaps you could direct me to an online resource covering this subject.