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Author Topic: Hacking Bitmain Antminers (S7 & S9) because man a lot of these break......  (Read 1677 times)
SpatariuM
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April 22, 2018, 05:03:29 AM
 #81

Hy all,
Fairly new to this forum so don't take my words as reliable. Smiley
I recently bought a dead S9 hashboard to play around with it. (I do not own any complete miners, but a verry curios person I am Smiley )
It is a autotune version from March 2017.
Some notes to sumarize what you all have written in the previous posts: powerwize- there is one string of 21 chips in series with 3chips in paralel for each step (63 chips total); comunicationwise- 63 chips daisychained.
 If one chip goes bad and pulls any clock or data line to ground, the board is dead. Same situation if a chip interupts any af these lines.
Nice thing is that Bitmain has included testpads for each chip, so troubleshooting is fairly easy.
O this board, powering it up by itself, does not do any good. I get 0.38v at the buck converter output. (I am thinking that by missing the 3.3v line the PIC is not powered on, so no output).
Removing the heatsinks off the chips is easy if using hot air, so is scaping the leftover thermal adhesive from the chip by using a
hot soldering tip.

(Correct me here please) Measuring for short on the powerline steps with resistance setting on my meter is not helpfull because the chips have a verry low resistance, under 1 ohms each... I also noticed some resistor paralelled with each step of chips noted R500 wich would make measuring for shorted chips a bit harder.

These boards are missing some back heatsinks near the intake fan(12 to be exact), so overheating in this area is a posible reason of failure. (The 2 changed chips on this board were located precisely in the middle of the heatsinkless area).


I think I was lucky enough to buy a board that someone has allready attempted to repair, so the guy has replaced 2 chips. Unfortunately for him the resoldering process was not good, therefore some pins were not soldered to their pads.
After resoldering the 2chips, all measures tell me that the board is fixed. I am now sad that I removed all the heatsinks glued to the chips, as for further tests, I will have to clean all chips and reglue the heatsinks.
I have also an idea of repositioning the back heatsinks in a chess like pattern, to see if this improves cooling at the begining of the board...
If only I had a controller to test it... Does anyone located within EU have a spare controller for lending it to me?
Regards,
Mihai

Electromechanical Engineer/Electronics hobbyist.
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SpatariuM
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April 23, 2018, 05:28:09 AM
 #82

Question : on a working Hashboard, when powering it up with only 12v rails and not conected to a controller,  is the red Tf led supposed to stay solid red?
 Ca someone who poseses god miners and defect boards test this?
This ,I guess, would be a quick and easy method to see wich board is defect on your machine when one board is going defect...
(And give me a hint when a repair was succeful or not)
 A solid red Tf led could indicate wheter clock and data lines are broken between the first and last chip on the chain and could prevent people from seeing "magic smoke" when trying to test boards...


Regards,
Mihai

Electromechanical Engineer/Electronics hobbyist.
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May 02, 2018, 02:23:10 PM
 #83

Question : on a working Hashboard, when powering it up with only 12v rails and not conected to a controller,  is the red Tf led supposed to stay solid red?
 Ca someone who poseses god miners and defect boards test this?
This ,I guess, would be a quick and easy method to see wich board is defect on your machine when one board is going defect...
(And give me a hint when a repair was succeful or not)
 A solid red Tf led could indicate wheter clock and data lines are broken between the first and last chip on the chain and could prevent people from seeing "magic smoke" when trying to test boards...


Regards,
Mihai

the boards i have repaired light up when they are connected to the controller and start hashing. when a miner doesnt detect the board i look for the one without the red led on and thats the one that failed...in my case at least. i could be wrong but i think the light only comes on when the board is being checked for connection to the controller....when the chips are being checked and tuned....and finally it stays solid when the miner is actually mining away. hope this helps.
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