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Title: Bitmain S9 control board repair ( fan feedback gpio related ) Post by: darkm4n on March 09, 2018, 07:53:41 AM Hi!
I got a S9 control board that seems to have the circuit for fan speed feedback broken, the board hangs at "Checking fans!". After measuring and trying to find the problem I concluded that the fan PWM and fan Feedback pins goes directly the CPU ( ZYNQ ), having those GPIO I/O failed it seems that the only solution is to replace the CPU. Do anyone else had problems with the fan feedback circuit ? Can someone provide the correct values for the two resistors and two capacitors near the fan connector ? From my measurements I got: R146 - 10kOhm, R148 shorted ( seems wrong, this resistor deals with speed feedback ), C200 about 2.7pf, C198 about 120pf. It is very difficult to trace the path to the CPU since it is a multilayer board... The board has 6 fan outputs, on my board measuring measuring from R146 to ground I got 10k, all the other outputs ( even those not populated ) are shorted to ground. When powered I get 3.3 volts on R146, that seems to be correct since it is the PWM control of the FAN, also got 2v over the fan speed feedback. Another helpful method would be to bypass the fan protection but it seems to be compiled into the Kernel, if anyone have a method to do this I am really interested. Thanks! |