1.After changing the low speed fan, the speed can not be recognized
2.The web page is no option to change the voltage
3.The noise will get bigger in a moment
4.I flashed two D3 is all that question
for some reason you are still on the default bitmain firmware. Please download again and flash this file:
https://mega.nz/#!P05C3TJT!x8oA-j4myy4jxX83cMcmkPscpotU0oAvMHJEbZ5IfZg
System -> Upgrade -> flash image