I'd like to warn people over here about Bitmain's poor customer service and poorly built products, as I'm waiting for a few months atm for a broken hash board of an R4 miner to get repaired. Moreover, their PSUs sometimes don't switch on at all, and you need to wait a few hours before trying to get them working again by pulling out the power plug and then putting it back in the wall socket again, and another S9 miner switched broke and it took a few months to get it working again. Bitmain, please fix your problems and train your support staff better, as the current staff seems completely unreliable to solve time-critical problems as which may arise with bitcoin mining. It might be superfluous to tell you all that we're still waiting for apologies and a fitting compensation for the damage this problems causes to our mining operation. @Bitmain: thanks in advance and don't hesitate to send a private message in order to get things working again!