MY BITMAIN RMA EXPERIENCEAbout a week ago, I received my first antminer unit from the first-round auction for a reasonable 4.75BTC. it ran well at 180GHash but had an extremely loud fan that reported its speed in the range of 4700-5500. I mentioned this in the forum, and bitmain quickly [and nicely] advised me to buy a replacement PWM fan that they would cover the costs of, as the noise and high speed appeared to be some sort of individual error. I installed a replacement fan with slightly lower CFM and virtually silent, and was quite happy. however, somewhere in this span of time the second board became unresponsive and would not show up or hash.
I tested the board as best i could - using a multimeter checked almost every accessible capacitor or point of voltage, and the issue appears to be within, or related to, the TI TPS53355 DC/DC buck converter, as the first one on the board was not producing any 1.10V output, whereas the other 3 were doing it successfully. Unfortunately, without the first chip working, the entire chain will not operate, and I requested an RMA/replacement as finding a local engineer to determine the issue and if necessary order the $>10 regulator would likely cost more and take nearly as much time as to be shipped a replacement.
BITMAIN shipped a replacement board alongside my second unit (from the group buy) and it arrived on thursday. It did not come attached to a heatsink (I was told it should, and am very happy i had not yet shipped back my bad board+heatsink!), but replacing it was straight-forward with the removal of ~16 screws. On removal, i noticed a slight issue with the application of thermal paste:
here is the backside of the dead board i removed, you can see that the paste was not under sufficient pressure in some areas.
Once the new board was put in place (I reused the thermal paste, but may need to buy a new tube and redo it as the temps are 2-4 degrees higher than the primary board), the unit booted up and returned to hashing perfectly.
The second unit installed like a breeze, with only one small exception - It came with the ip address
192.168.2.049. This may have been an obvious misprint to someone more involved with networks, but in my case it took almost 10 minutes of confusion before i realised it is actually
192.168.2.49 without the extra zero.
Now, both units are running well at 200GHash each (thanks goxed!) and i have installed secondary fans for both to impove airflow, and also put some thick paper over the top where possible to ensure the air flows across the entire length of heatsink. I still have yet to submit receipts to bitmain for promised compensation of the RMA shipping but have no concerns about them renegging. BITMAIN has done an awesome job of producing a stable miner with a strong frame and it has the least hashrate varience of any of my hardware. Add a dedicated user profile and email contact, and I have absolutely no regrets over my purchase!
PS: the new boards are a little different, namely [better] screw terminals and [inexplicably] unused pads for 4 largish capacitors. heres a picture for those interested: