can someone correct me,i heard that they sell refurbished miners
i really not sure a friend of mine said this to me he bought 8 miners and had to send back 6 and had to pay for shipping fee to resend them back
It is widely rumored that Bitmain will mine with a specific miner for a while THEN sell it as a "new unit".
They HAVE sold units specific LABELED as "used" in the past, usually older units, at a fairly deep discount - but since the S7 is still profitable at their electric cost they've not done such a sale since just before the S7 was introduced, on the S5.
They ARE widely known to have some serious quality control issues with the S9 model - if it wasn't significantly more efficient than any other model an "end user small miner" can easily get ahold of they probably would have nearly ZERO sales of the S9 by now.