My phone refuses to boot quite often. Sometimes it will boot up perfectly fine and run for a day - day and a half, or it'll lockup and then refuse to boot up again, OR it will just not boot at all. My power button seems to be unresponsive, and the only way that I can get some action out of the phone is by reseating the battery in the well.
What I think it is, could be 1 of a few things, or a combination of them - i'm not sure.
Scenario 1: While playing with the Hyperdrive tweaks, my phone was hung after running the Zipalign tool for over 20 minutes and I had to pull the battery.
Scenario 2: I'm deployed on a ship currently, and I have my phone in a high-salt enviornment and I'm afraid that there might be salt corrosion inside of the power switch or the USB connection - shorting it out. I took my phone apart tonight and cleaned both items with isopropyl alcohol ( the switch itself on the main board ) but that didn't seem to produce any new results.
Scenario 3: I was recently rooting a Kindle Fire HD 7" for a friend out here, and I was dumb and didn't realize that I was pushing boot loader files that were designed for the Kindle Fire and not for my Galaxy S4. I have since tried to enter recovery, but with little avail. Download mode is also out.
A description of what my phone does when I reseat the battery: My phone will vibrate, the Galaxy S4 logo will show for 1.5 to 2 seconds ( same for download mode ) and if I hold the appropriate button, ' Recovery Booting.... ' will display as well. At that point, my phone will shutoff and the power button will become unresponsive.
If anyone can give me a bit of guidance on how to proceed to repairing my phone, I'd be super grateful.