[General Questions and Answers] jheller:
Containment: remove battery for more than 5 minutes, phone then boots without issues.

Known solution: I don't have one yet for my phone, but could a stock RUU fix it?

Happens on a HTC Desire SV, but I read there's more phones who have the same issue, but no solution yet.

Have the same problem?

- You can leave a reply with details about your situation. Have you rooted you phone, flashed roms, etc? This could help pinpoint the problem and search for a solution.

- Which brand / type do you have? You can vote which brand of phone you have with the same issue. I've listed some popular brands. This could indicate if it's related to one specific brand/type or not.

Other observations and possible explanations:

- Happens after turning off the phone. Possible issue here: is the phone failing to shutdown properly, leaving incorrect code or data in memory?

- Does not happen when restarting the phone.

- Does not happen when switching off the phone with fast boot option (in Settings > Power). There's reason to believe HBOOT is bypassed in this fast boot mode, as it would take more than 2 seconds to go from the black screen to the boot logo in normal boot mode, and in fast boot mode this black screen takes far less than 2 seconds.

- Phone vibrates 7 times after a couple of minutes. I see several hints on hardware failures on the forum: EMMC, overheating CPU, see related issues below. Both do not seem to be the case, since the phone is able to (re)boot containment.Open question here is what does this boot error code mean, and is it part of first or secondary (HBOOT) bootloader? See also next observation:

- Screen remains black when attempting to power-up. This could mean we do not get passed HBOOT. Possible issues: kernel can not be found by HBOOT, or HBOOT can not be started. Again here, it could be interesting to know what exactly makes the phone vibrate 7 times. Is it HBOOT, or firmware?

- Removing the battery for more than 5 minutes solves the issue. Does this mean the phone boots differently when it's just restarted, when it's booted from power-off, or when the battery is pulled and then started? I can think of two possibilities: that the phone attempts to boot from incorrect code in RAM, which is being wiped after the battery is removed long enough, or that some CPU pins remain high when the battery stays in the phone, causing the CPU to boot from another location. Room for thought here as well.

- CWM recovery is flashed, the phone is rooted, but still S-ON. Going back to stock recovery did not fix it. I have some doubt believing that flashing a custom recovery partition can cause something to happen to the boot partition, although in my case, I see the boot partition is located right after the recovery partition. The CWM recoveries I flashed, were about 5MB, while the partition it's placed in is more than 8 MB. So plenty of room to fit CWM recovery in.

Related issues:

- Overheating CPU. Most likely not the case here. Phone does not feel hot at all, never had freezes and such when using the phone.

- 7 times vibrate during welcome screen or even after that. In the case above, the phone doesn't reach that far.

- Hard brick. Issue described above can be called soft-brick maybe. Pulling the battery for more than 5 minutes fixes it until the next shutdown.

That's all I can mention, maybe this is already helpful to some, most certainly when you gave up on your phone thinking it's hard bricked.

So pleae leave a message if you like this thread, hit thanks, and/or vote for the brand that you have the same issue with, and maybe this leads to the solution,