Phone went for a swim and the power button went kaput
1 - 2 horas
As you may already know, phones and water don't mix. I fell off of my dock into the water with my phone in my pocket. Fortunately, I wasn't in the water for more than a couple seconds. Still, my phone was soaked. I immediately pulled off the cover and tried to power off the phone. Which, in retrospect, may have been what caused the problem. Then I plopped the phone in a bag of rice and hoped for the best.
After a day, I took the phone out and tested the phone. Amazingly enough, the only obviously problem was the power button. I couldn't power the phone off nor could I do a screen grab. On the whole, fairly minor inconveniences. So, I just left well enough alone and live with it.
Fast forward a couple months later and the power button starts acting up. Randomly 'pressing' itself and trying to power off. After researching the problem in iFixit, I've narrowed it down to the power/sensor cable...I hope.
The repair went well. My phone is once again 100% functional. I couldn't be happier.
It took me about 2 hours, but I went SLOWLY and labelled every screw that came off.
Flashlight. It may have been poor lighting in my work area. But a flashlight saved my butt a couple times.
One of the screws that holds the power button to the frame is a PITA to get to. I ended up using a really long screw driver to get the right angle. Even then, I really had to bend the cable back covering the screw.
The instructions say you'll need a new speaker. But if you remove the speaker slowly, you can save the adhesive. Also, the stand-off for the proximity sensor has some adhesive on it. If it sticks to the old power cable, use tweezers to transfer the adhesive.
P2 Pentalobe Screwdriver iPhone
Essential Electronics Toolkit
iPhone 4 Earpiece Speaker
iPhone 4 (GSM/AT&T) Power and Sensor Cable