Help S2 i9100 battery drain even when turned off

[ursal666]

Hi,
hope you can help me with this!
a month ago my battery started to drain reaaally fast. It would last 3-4 hrs either used or not. Even turned off!
Battery doesn't seem to be warmer than usual, actually it's quite cold, and so it's the phone.
Tried to replace firmwares (from 4.0.3 to 2.3.6 to 4.1.2 to cyanogenmod. stock kernels and not siyah and dorimanx). Tried to replace the usb flex cable. No change. Of course I replaced the battery, not difference except a slightly lower drain (new battery permorms better).
Tried to selectively disconnect all parts (sim, sd, lcd, buttons, cameras).
Now, what could it be the issue? Should I remove the motherboard and check... what should I check XD?
I am using it in Italy but it's originally French.

Any ideas?

 

[togger161]

If the battery is draining even when the phone is off, and not just screen off/deep sleep, then it does seem like a hardware problem.

I had a very similar issue with my HTC Desire, battery would run totally flat in 7 hours with the phone turned off. With my HTC, I think the problem was moisture, it had been in my pocket when I got soaked whilst out walking. Never got any rain directly on it. I gave up on it, purchased an S2, only to find out a week later the phone started to work fine. My wife now has it.

Draining the battery whilst off eliminates any software issues such as rogue apps. Different roms will not help either as nothing is running. Would definitely be looking for a hardware issue if it were me.

 

[ursal666]

Thank you very much for your answer.
Hardware problem is my guess also. In your opinion, could it be an option to remove the motherboard and for example clean and remove/put back parts?
Since I selectively disconnected all flex cables (and replaced the usb one) I narrowed down the culprit list.
I am familiar with computers, but not with phones. Does it sound reasonable (don't even know if possible) to remove and put back cpu with some thermal paste or... you tell me what! =)