[AT&T, Rogers, Bell, Telus Samsung Galaxy S III] Top5a:
The best part about spending 30 minutes typing a post is having your browser crash. Anyway, if you have any further questions because this is going to be a bit brief, let me know.

My background: Fairly well-versed in Android, custom ROMs, flashing, rooting, doing development work on Android, reading directions, decent google-fu and RTFMing. But I really need help on this one. The phone in question is my primary phone, which I actually like to keep as stock because I don't want anything mucking up on it. It's 20 months old (daily usage), running stock 4.1.1, which was rooted about 17 months ago with cf autoroot, which I needed for development purposes. For the past 10 months, I have been using an extended aftermarket battery, because when traveling and thusly using navigation, gtranslate, lots of messaging, and whatnot with a bright screen whilst outdoors, I was tired of having my phone leave me without a communications device at 8pm.

Recent changes to phone: Several weeks ago, before another bout of traveling, I did my usual *#197328640# perso256 disable (one of the reasons that I like keeping my phone at 4.1.1), and voila -- carrier unlock.

What happened: Things were going swimmingly for a few weeks, when one day, I was out and about, typing something into google translate, and the screen just went black. It was early midday, and the phone was at 90% battery (extended battery life ftmfw). Every now and then, when doing serious multitasking (and, mind you, since the early days of owning this phone, as well as through the entire life of my GS1, which still works, by the way), my GS3 would occasionally reboot of its own accord. I thought nothing of this, except it just being a hallmark of samsung phones, and a minor inconvenience, at worst. This time, however, it failed to power back on. I removed the battery, held in power button in an attempt to discharge any residual power, and put the battery back in. Nothing. Panic. No ssung logo, no vibration, no lights, nothing. Just the black screen staring back at me. There was no moisture, and no trauma to the phone... nothing, save for a ridiculous sinking sensation.

Symptoms: Phone completely unresponsive. I tried a charged stock GS3 battery, and the symptoms are the same. If I plug the phone in without a battery, the led lights up red for a time, and that's it. Even though I haven't modded this phone at all, with the exception of the rooting almost 2 years ago, I tried everything I could think of and read online. vol up + power + home. vol down + power + home. Leaving the battery out for a while. So much reading through these forums and some others online. When I plug it in in windows (even though I primarily use linux), I get the QHSUSB_DLOAD problem, so I do not think it is a problem with the power button? Or maybe the power button can be permanently depressed or something that would cause this? Anyway, I've installed QHSUSB_DLOAD windows drivers, but don't want to start flashing things until I know there isn't another longshot option to get this to work. I even loaded up linux and ran pblclear, which allegedly attempts to knock HTC phones out of being stuck in QHSUSB_DLOAD mode. Didn't work, but figured it was worth a shot, and seemed relatively harmless.

Why I don't even know if it's SDS: The reason I'm asking this is because I'm completely at a loss. SDS appears to affect i9000s after 150-200 days, OR when people incorrectly flash a ROM, or something happens during flashing or modification. My phone is an ATT i747 has been fully operative for 600+ days, and I haven't done any flashing, rooting, whathaveyou in nearly two years (and it was just that simple autoroot that I ran once).

What I'm wondering: I really want to get this phone working, because of hundreds of images, notes, data, etc. that I have accrued over the past few years. Most of my videos and larger files were on my sd card, but literally hundreds of memories and works in progress that I would do insane things for were saved to the phone. I'm an idiot for not backing it up, but I wasn't doing anything to the phone, so wasn't expecting such a catastrophe. Will JTAG work? What about a debricking microsd image? Most of the ones I can find are for 4.1.2 or 4.1.3 -- are there any for 4.1.1? I'm nearly certain 4.1.1 is my version, because IICR 4.1.2 and 4.1.3 don't even have the perso256 disable menu, and it's why I had not upgraded to them. It seems like the microsd rewrites would wipe the contents, and then I would have to quickly attempt a recovery on the data? Or have there been any cases with similar failures that are something else dying on the board? To be perfectly honest, if it appears to be an issue with the board, it's not beyond my ability to perform BGA rework and remove the emmc entirely, and transplant it onto a new board, but I would ///really/// like to avoid that.

Thanks for reading... :angel:

Edit:

Additional information: I forgot to mention that I have found pages such as this samsung-galaxy-s3-sgh-i747-i747m-repair-dead-boot-1755452 [I'm afraid you'll have to google it because I can't post links if you want to look TT^TT] which have files that say, for example, "Samsung SGH-I747 Repair Boot Supported" if using JTAG. So, if there aren't suggestions about how I can fix my phone with an sdcard unbrick, or something else, does anyone know whether or not doing a boot repair will unbrick a phone without wiping the ROM itself? Thanks again~~