I would agree with using your hand to investigate.  What I did was use two fingers extended out over the edge over the back fan and the front fan.  I would move my two fingers (index and middle finger) around the edge in a circular motion until my fingers were at a point where the noise was no longer audible.  Once I found the location where the air being sucked in was no longer audible, I placed only one finger (my index finger) over the same spot and the sound was still no longer audible until I moved my index finger to another location.  So, I was able to find the "sweet spot" to place the tape on the grille of the intake fan in front.

Every rig does not have the radiator type heat sinks in the exact same location on every chip.  Some could be off or aligned in a certain way after manufacturing that allows for a whistling sound as wind is sucked in between the fins of the heat sinks when they are positioned just right.  Since every rig does not have heat sinks in the exact same location and the exact same size [varying by thousandths of an inch]... this whistling noise is audible only on a small percentage of rigs that have these heat sinks aligned just right to allow for this audible noise.

This is why I feel a small piece of tape is sufficient to reduce the amount of air across particular heat sink(s) causing the noise.  I noticed one miner had placed a piece of foam on the shelf in front of the fan to reduce the noise because that just happened to be the location on his particular S7 where heatsink fins were aligned just right to allow for the whistling noise.  The location of where the wind rushes in across heatsinks will vary from one rig to another more than likely.

Damn...

Really?

So, PayPal did not help or eat the cost?

Unbelievable...

It's 1293 watts at the wall for the boards, fans and controller at 25 degrees Celsius ambient temperature.  Batch 8 is approximately 400 watts per board at default frequency of 700 MHz.  The HX850 can actually push more than 850 but not recommended.  I would think you would be fine without over clocking.  However, you might want to ask dogie or someone else who is very familiar with this PSU.  Shoot dogie a PM.  You will find a forum he created about PSU's here: Dogie's Comprehensive Power Supply Analysis:  

Sounds like it's time for you to go to the following thread to place a bet:

Diff thread Nov 23 to Dec 7 Set up stage- Picks Open!

Understood.  Thanks for the link.  I see what you are referring to now regarding fan malfunction instead of internet malfunction.

EDIT:

This post made by BITMAIN is what had most all of us believing the October Firmware update was possibly a fix for internet connection blackout.  He does advise us getting a second ISP for a good reason apparently:  So, I suppose I should have paid more attention to the "exclamation point" at the end of his statement regarding making sure "you do not lose internet connection!"


EDIT #2:

I can see now why an update to the October firmware may be beneficial since it may address the issue of a fan malfunction instead of an internet malfunction.  Now, my only concern is updating firmware for batches of S7's with frequencies higher than 600 MHz.  The present firmware updates available only go as high as 600 MHz.

Here is only one example [from page 199] of several listed in the forum [I'm not going to take the time to look up the others on other pages in the forum.]:


I KNOW Biodom is NOT making this up.  His internet blackout was only a short time.  How long is short?  I don't know...

If anyone wants to test this out for us by disconnecting internet from their S7 [with October firmware] and leave it disconnected for two hours or more, be my guest.  I'm not testing it on mine.  I don't want potential delays from having to send boards back for repair/replacement.  

I personally will not upgrade anymore S7's I purchase in the future unless it is necessary for some major fix.  Even if my S7's arrive with an updated firmware other than September, I'm setting my fans to manual.  Period...  It's not worth the risk.  If they take away the ability to manually set the fan speed, I will connect the fans directly to a PSU.  It's just not worth the risk.

Switched PDU(s) and Teamviewer with an extra computer on premise is an easy way.

I haven't bothered under clocking any of my S7's yet.  All of mine are default at 625 MHz and lower.  So, you never lowered the voltage when under clocking your S3's?  If the voltage was changed, the S3 had to be rebooted.  Same goes for the S5. 

I didn't know the S3 had that option.  It makes sense if one has cheaper power rates at certain times during the day.

If such an option is available, what tab would it be under?  If you can show it on the S3 with a screen shot, it would be helpful.

4400 RPM's is about the limit of these particular fans.  4500 RPM's might be the limit.  I would think at least 3700 RPM's would be sufficient to keep the rig from burning up if the internet was to go out on you.  Of course this depends on the ambient.

Most certainly...

I believe the S7 will probably be around as long as the S3; in terms of still making profit, for as long as a 2 year period or longer.  If I were to get Batch 8, I would under clock to 650 MHz.  My opinion.  Others can do as they wish.

EDIT:  I'm going to "baby" mine to the fullest.   

I don't see myself pushing any S7 higher than 650 MHz.  Simply for the reason you said, for the longevity of the rig.

EDIT:  If it comes with a default higher than 650 MHz, I will under clock it to 650 MHz.

I will share with you the same thing I have told someone else.  I'm sure others will agree.

There is nothing wrong with the September firmware.  The October firmware SUPPOSEDLY fixed the issue with rigs burning up after internet loss.  I've seen two people in the forum who have had their units replaced because of burning up after losing interest and they had the October firmware.  One of them lost 3 rigs due to burning up after internet loss.  

Don't believe the hype about the October firmware.  It does not fix that issue.  It's not worth risking a $1,700 to $2,000 investment depending on the firmware having fixed that issue because it hasn't.  Your investment is safer if the fan is set to manual with a setting of 75% or higher.  It may be less than 75% is okay but that depends on your ambient temperature.

I'm keeping all of mine from now on with the firmware they come with and setting the fans to "manual" to avoid burning them up if the internet goes down.  We already have confirmation your rigs will not burn up if you have the fans set to manual at 75% or higher.  It's possible they may not burn up with the fan set at lower percentage but 75% is the lowest we have confirmation of thus far.  

The S7 is an EXCELLENT rig in many aspects.  The only issue [in my opinion] is the risk of burning up the rig during a long period of internet failure.  How long?  Who knows...

BITMAIN is still installing the September Firmware and probably mining with the September Firmware on their own personal rigs.  If it was so important, I would think they would already have the updated firmware pre loaded.  Even if they were to have it pre-loaded, I would not risk a $1,500 to $2,000 investment on this issue. Go to manual with the fan and do not trust the firmware update to fix the issue.  That's my opinion.  

Do not upgrade to any firmware you see on Bitmain's support website at the moment.  It is for 550 MHz, 575 MHz and 600 MHz only [That would be batches 1 through 6].  If you upgrade your Batch 7 [Which is default at 625 MHz] to one of the other firmware, you risk changing the default frequency of your mining rig and can potentially shorten it's warranty period if you bought other S7 batches prior to batch 7.  If something goes wrong with it during the warranty period [But outside the warranty period for previous batches] you may be out of luck because they think you are trying to get an earlier batch [That's out of warranty] serviced.

Yes, they will.

After seeing the temps of your boards in the rig, I would set it to whatever percentage keeps the RPM's where they are now.  That may be at 80 to 85 percent.  They mine better between 50 and 60 degrees Celsius.  That's where it is now.

Agreed

I don't know the answer to your previous post about cgminer.

Thanks for your opinion.  I believe I will leave it alone.  I tend to believe the Sept. Firmware version is probably the best while maintaining a manual setting on the fan speed.

Batch 7 after 1 hour 10 minutes:

When you hit the reset button does it revert to the 9/15 firmware?
[/quote]

I have yet to hit the reset button to find out.  I know my S5's and S3's retained the firmware version I upgraded them to after a hard reset.  I would expect the same with the S7.

I agree about there being only two machines with varying frequencies as the default.



Thanks for the info.  I feel more at ease about my rigs surviving an internet outage.  I suppose I should raise those I have at 60% to at least 75%.  My S7's have varied in terms of core temperature.  Those I have presently at 60% were running too cool at 70 and 80 percent.  Which resulted in a few GH/s slower hash rate.  When I keep them between 50 and 60 Celsius, they seem to hash better with lower HW errors.

My batch 7 @ 625 MHz & 5.0 TH/s was delivered about 30 minutes ago.  I've had it running about 15 minutes now.  It had high HWE's when I first turned it on.  Once I configured the pools the HWE's went down to 0.0027% and remains there now after 26 minutes of mining.

My kernel log is blank like yours.  I hope this fixes itself somehow fairly soon.  I do have Tue Sep 15 16:50:19 CST 2015 Firmware.  I'm about to update firmware.  I'll edit soon to let you know what happened after firmware update to Oct. version.

EDIT #1:  Well, I'm a bit hesitant about upgrading firmware to October version because they do not have one for 625 MHz rigs posted for update.  I'm concerned it would make the default frequency 600 MHz instead of leaving it at 625 MHz.

Any opinions, anyone, about upgrading firmware for Batch 7 at 625 MHz default frequency?

EDIT #2:  I had a look at the kernel log on my other S7's that have the Oct. Firmware.  Some of them have data in the kernel log and some do not.  Interesting...
I'm not going to update my Batch 7 to the latest firmware until they have a version posted for rigs with 625 MHz available.  I do have my fans set on manual @ 80%.  It's 75 degrees outside at the moment.  So, the AC is on in the house right now.

EDIT #3:  I did a soft reboot on one of my earlier S7's with a blank kernel log.  They are back to working and showing data in the kernel log.

EDIT #4:  I did a soft reboot on the new Batch 7 and the kernel log is fine.  So, it sounds like you just need to do a soft reboot.

EDIT #5:  Don't be alarmed if your hash rate is around 1300 to 1700 GH/s after a soft reboot.  This means only one board is hashing.  Just soft reboot again and your hash rate should go back to normal and the kernel log still displays data.  I had to soft reboot my Batch 5 twice because of the same issue with 1300 to 1700 GH/s after the first soft reboot.