[Xperia SP Q&A, Help & Troubleshooting] Cyanoid:
I am posting this update in aid of future Xperia owners:

Problem: I seemed to have experienced the infamous Xperia "Red Light of Death". Phone vibrated 3 times continuously when charged. Screen never came on. Led was only ever RED, and only came on sometimes, sometimes solid, sometimes blinking twice. Computers were not recognizing the Xperia. Neither volume UP or DOWN button presses were ever recognized by any software on either the Win 7 or Win XP installations. However, on a couple of occasions, both computers recognized there was a device on the USB when doing a reset (reset + power). This caused them to try to install drivers. But the drivers, if installed, did not successfully allow any of the software tools to recognize the phone. Nor was the phone recognized in Device Manager, when connected, even when the UP or other buttons were pressed at connection time.

I asked for assistance on 4 or 5 of the net's biggest android forums on this... none came. So I was quickly giving up hope on the Xperia, since it seemed like there was nothing else to do. It might have taken water for all I know, when it was not in my hands, and the mobo might be quiched.

Solution: The phone is charging right now, the screen and color LEDs work fine, the original system is fully intact, and I did not need to reflash a new ROM or anything. However, I'm not exactly sure how I resolved the problem. I'll go through *some* of the steps that preceded this breakthrough. The breakthrough may (or may not) be due Sony's "PC Companion". This is an older version of what Sony now calls "Xperia Companion" (which did nothing good for me, so I went with the older software). "PC Companion" was also useless to me, since it kept insisting on not working unless you allow a connection for it to update itself. But the update always failed, with no clue as to why, despite a/v & firewall disabled. I found a comment where one user said he was able to do a bit more with PCC, once internet was disabled. So I tried that, and yeah, I could at least convince PC Companion to see if it could recognize the phone once the internet was disabled. But just like Flashtools, adb, the Sony Xperia SP drivers and all the other tools, it didn't recognize the phone was plugged in. At least, not the first few times I tried it, using various button combinations. (Up, Down & Reset/Power). Finally, I got a blue light and the PC (Win XP install) started loading drivers for the device.

I'm just not sure what triggered the change. Was it a reset/power combo operation? Was it a slight shift in the motherboard or USB connector that did it? Was it due to (the THIRD install of) PC Companion, or it would have happened with other software eventually? Its hard to say. I think these things contributed to the solution: PC Companion, the reset/power combo press, and just a lot of perseverance, most importantly. (3 days working at it in my case!). If you get this same problem with your Xperia, good luck to you.

(Trust me. You'll need it).

Lent my Sony Xperia SP (C5306) to someone, and it came back in a state where it vibrates 3 times when powering on or charging (it stops vibrating after a while, then starts again). And it won't boot or show anything on the screen, and only a RED led light comes on occasionally. So now I'm stuck on trying to flash a stock ROM on a Win7 system, using Flashtool 0.9.18.6, after installing the Flashtool drivers for "Flashmode" and the SP model, and PC Companion (PC Companion didn't fully install, because it demands updating, and fails on the update -- despite no antivirus installed, and the Windows firewall set to "enable all'). So now my problem is Flashtool won't recognize the phone on the "Please connect your device into flashmode" step, when I press Volume Down before reconnecting the USB cable. I've even tried taking the battery out for a few minutes, no dice.

At a certain point, after hitting the reset button and other buttons, Windows finally recognized there was a phone connected, and automatically installed USB drivers. Yet despite this, Flashtool still wouldn't flash the ROM. I do get 1 error in red saying "ROOT: THIS BUNDLE IS NOT VALID". Presuming this refers to the ROM, I made sure it specified it was for my model (C5306) and its even from the original carrier (Bell). In any case, it still goes beyond that error and proceeds to prepare the files for flashing.

So I'm not entirely sure what's preventing Flashtool from recognizing the phone, since it could be many things. My best guess is the soft or hard brick condition its in: since you can't power down the phone properly, and removing the battery is apparently not the same thing, its not getting to the trigger point that activates Flashtool's flashing. I'm right now trying the "rubberband trick". The idea is to keep the Volume down button depressed with a rubber band, and eventually, the battery wears down and maybe Flashtool recognizes it when it bootloops. I don't get that though, since Flashtool requires you plug the phone in via USB. And if its plugged in via USB, the battery should not ever run down, since its being charged by the USB port.

The phone was rooted, and IIRC, I think my bootloader is locked, so let's assume that. Can anyone help me along on this?