I've owned hundreds of Antminers in the past year.  Presently I have 100+ of which I run approximately 25 at any given time.  ALL are on mobile racks and each rack mines a different algorithm/crypto.  I can mine ONLY two racks at a time due to electricity availability at my operation.  

Anyway.  I just spent the last 8 hours trying to diagnose a restart/reboot situation on an Antminer Z9 machine that has been running flawlessly up until yesterday.  Suspecting a bad hashboard, I unplugged ALL three of the hashboards and ran the machine with ONE at a time plugged in.  All three hashboards were fine and the machine would run fine with only ONE plugged in at a time.  BUT, as soon as any "two" were plugged in, "poof" restart and reboot every 60 seconds.  

It was through this posting that I decided to swap out the power supply and "VOILA"!!!  Yes INDEED, a faulty power supply that APPEARS to be working fine can be a "RESTART", "REBOOT" issue when this occurs.  The Antminer that I swapped out the power supply for is once again running LIKE A CHAMP!!

Yes, I do own "several" multi-meters and in the future, I will expedite this diagnostic "scenario" in the future.  If this ever occurs to me again, I will do DC VOLTAGE and DC AMPERE measurement before spending hours and hours and hours of "lost" time before swapping, plugging, flashing and pulling my hair out again!!  It's 8:00AM here, I started on my "restart/reboot" issue 10 hours ago and THANK GOD IT'S FIXED!!!  Drinking two pots of coffee and staying up ALL NIGHT to fix a machine is no fun!!

THANK YOU FOR THIS POST!! It's been "GOLD" in helping me find the solution to what could/should have been a very simple diagnosis for me.  The difficult problems I solve easily; the simple things take me a while..  

THANK YOU!!!  
THANK YOU!!!  
THANK YOU!!!  

Old`RADIO

Hello Gentlemen...

"WHISTLING": in the Antminer S9...

MYSTERY SOLVED...

Well, I have owned hundreds of the Bitmain Antminer S7's, S9's and S9i`s.  Last night while re-purposing my Antminer S9 machines, I ran across "ONE" machine that was giving me the horrible "WHISTLE".  Unaware that this is/was a problem, I first thought it might be a fan issue.  I have tried four different style of OEM fans.  The "whistle" is internal to the placement and configuration of the heat-sinks on the hashboards.  I tried swapping all three of the hashboards in each other's slots and the whistle did not diminish.

After swapping FANS, CASES, FAN MOUNTS and HASHBOARDS,  I finally was able to discover the cause of the problem.  When I swapped hashboards, The whistle did noticeably diminish when I replaced one of the S9 v4.317 Hashboards with a S9 v4.21x hashboards.  I looked at both hashboards to see what the difference is/was.

The EARLY model of S9 machine hashboards have a straight cut large heat-sink where ALL of the fins protrude straight "UP".  Bitmain changed the design on the large heat-sink design from straight cut (all fins UP) to a large heat-sink with a CENTER FIN WITH A "FLAT TOP" design where the center fin has a "HAT" on top of the center fin.  
Think about it this way.  A police whistle uses forced air that produces a whistle when it passes over the sideways "slot" cut into the exit port of the whistle.

So, the whistle is caused by the forced air passing over the "new style" heat-sinks (center fin is a flat top) and creating a high-pitch whistling noise.  It's more noticeable when the machine reaches the "premium" air flow speed which allows the air-flow to reach the optimum speed that interacts with the heat-sinks center fin "flat top" to produce the high pitch whistle which is so, so, so annoying.  Also, when fan speeds are ABOVE and BELOW the optimum "WHISTLE" speed, the whistle will increase or decrease.