How can I fix my broken power button?
Recently my power button had stuffed up and everytime i use it i have to take the case out and use my fingernails to press it as hard as i can to turn it on.
I confirm Etain's solution: the pill blister trick works perfectly for power & volume buttons. You can try without opening the phone but the best way is to open it (only 8 screws!), so you can position precisely the pill-blister and even secure it to the case using a bit of adhesive tape. My Lumia 520 works like a champ since I fixed it this way months ago. Go to youtube for tutorials!
Well everything goes bad eventually, anyway get a junk phone just like yours and steal the keypad off of it. The spring is broke under the button and or is misaligned (which you could take off and put in another,but very hard to do w/o losing all the parts to the other buttons) And then being very very careful when swapping out ,cause the mini parts are crazy small.
Manually repairing the Lumia power button may void your warranty. I'd recommend you to take it to the nearest Nokia Care shop and ask them to repair it for you. Most probably, they won't charge you any money as its still in warranty period.
Hope it may helps you!!
I have the same problem with the power button. It somehow broke off and I am not able to power off the phone causing my battery to drain very quickly. It doesn't pay to have this fixed because the cost of repair is almost the same price as a new phone. The phone still works but who wants a phone that is in constant charge mode! These Lumias are inexpensive enough to buy a new one, that is if you like the phone enough, and I do.