Hi,
my S2 suddenly stopped after have been working for few weeks. Now it shuts down in few minutes after powering on.
I also wrote to Bitmaintech, but yet not got an answer, so I did the following:
1) Reset the settings to factory defaults - not helped.
2) Updated the firmware - not helped.
3) Downclocked the frequencies - yet no success.
4) Removed 1 blade - 90% hashrate, but it started to work.

Now I'm waiting for BitmainTech's support  response.
 

So, you may try to just pull out 1 blade for now..