Hey, Josh, thanks for replying, but I'm not that sure about the LCD, cause everything but the GPS was working fine before the oven (and I didn't touch on it (LCD) to remove the main board). One thing I noticed is that the issue is related to the charging process. Sometimes the phone was working great, and just after charge it or connect to iTunes, the "white screen" started to appear. So, last night I did something that I had not done yet: let the battery completely dry and put it to a full charge. So far so good, the iPhone is working fine since then, there's just 30% of charge right now and no white screen untill this moment. Hope the issue has gone, but I'm not all confident about that, since I didn't test connecting to iTunes (I charged the phone at the wall plug). Guess I'll let the battery dry by complete again and then let it charge and sync with iTunes. Let's see what's gonna be! Thanks again for the attention.
Hey Fasthans, thank you so much for your attention! Actually, the "White Screen of Death" started after I did the "Oven Trick" - took off the motherboard and put it in the oven for 7 minutes at 190 C -, to fix my not working GPS (it was able to find location only by triangulation/Wifi, the blue dot was not pulsating anymore). The oven's heat can melt the solder joints and put your fault hardware back to life. And it impressive done the job, the GPS worked again! But after a month, the white screen started to happen always after the phone went to sleep state. So, I don't know why in my "smart" mind, I thought that the oven trick could help fix the white screen and (maybe) the camera issues. Great, did the procedure again and, this time, I was able to brick my phone! It's stuck at DFU mode and can't restore anymore. Doesn't matter if I try a "Shif + Restore", a straight Apple restore or a qpawn DFU state to recovey. I always find an "Error 1600", or iTunes shows "Preparing iPhone to restore" and stops there,...
I had this problem with my phone, but in my case the issue were the solder joints in the motherboard (PCB). I took it off and put in the oven for 7 minutes at 190 C, then, my GPS started workin' great(the oven's heat can melt and fix cracks in it). But in your case, as the GPS was fine before disassembling it, my guess is that should be something connected wrong. You changed the screws, but did you put then in the right place? You can't exchange them, every screw has your own place. Check the Wifi/GPS antenna connection (close to the battery connector) too, maybe it's not well fixed. At the top cover of the phone are five screws, the 1.4mm Phillips (step 7 - http://tinyurl.com/43aon77) has a nut under it that use to fall when we make some movements with the mainboard. If that happens, the contact between the screw and the PCB is lost. Try to check it too.
I already had this problem when disassembling the phone. In my case, I just cleaned (with alcohol) the digitalizer contact (both, the one at the PCB and the connector cable itself). After doin' it, I let the phone opened for a while to let the alcohol dry by complete. Touch sensor working fine since then. As said before, don't forget to take a look at the screws positions. They just can't be mixed up, every screw has its right place.