This is a good deal people. You cannot buy this much hashing power for this price anywhere in the world. Bitmain consistently out prices everyone. These S4's will be good to run for 10 months at least with underclocking later on.  We need 50 more S4's. P.S. Thanks for the rapid PSU replacements. We had several go out right away and Yoshi took care of us fast. GO BITMAIN

I upgraded all of my S4's to this firmware and gained at least 5% hashing speed on the pool. I also set difficulty to 2048. 225 Mhz 0725 volts . They are all hashing at least 2200 and are stable meaning I don't have to hard reboot them every day for crashed chips or reduced hashing speeds.

can antminer s4 use 220v. electricity?

Looks like your hashrate dropped to 0 over 14 hours ago.  It just took that long for your average to get below 1500.  I upgraded all of my S4's to the latest firmware (Oct 16) and have not had any issues, except I needed to reboot another time after the firmware upgrade, on all of them.  All of them ran poorly after the automatic reboot from the firmware upgrade.  But I always set the difficulty manually when the option is offered by the pool.
 
Do you know how high the board temps are getting?  The UI shows 50-51 now, but it hasn't been hashing.  I've seen this (hashrate drop to 0) happen with temps in the 60's.  They should be able to handle 60, but I'm just passing along what I have seen.  I have also seen this happen when trying to overclock with stock PSU.  (I can see in your screenshot that you are not overclocking, but wanted to mention it anyway.)

You should setup some kind of alerting.  You don't want to lose half a days worth of mining on an S4.  There are a couple home grown monitoring programs out there.  They require a bit of work to set them up.  I see that Justin Ramos shares open-source monitoring software.  I don't know him.  I have tried his P2Pool code, which is good and has extra reporting.  I intend to try his monitoring solution.  I think you have to install 3 software packages.  The API client, the manager, and the monitor.  https://github.com/jramos

I also ran across this site, if you want fast and easy.  http://www.awesomeminer.com/   There is a one time charge for the version that send notifications.  There is a free version to try.  I don't know this site and am not endorsing them, but their product looks good.  If you search for "bitcoin mining monitoring", you will find others.

I upgraded all of my S4's to this firmware and gained at least 5% hashing speed on the pool. I also set difficulty to 2048. 225 Mhz 0725 volts . They are all hashing at least 2200 and are stable meaning I don't have to hard reboot them every day for crashed chips or reduced hashing speeds.

I have a S4 B1 and S4 B2. The S4 B1 is working great but the new B2 that i got in a couple weeks ago worked great for the first few days now I cant get it to hash more than a couple hours. The box would stop hashing but it would stay on, the fans on with a blank (but lit) LCD screen.

I re-seated the SD card and it worked for about 10 hours and started doing the same thing. It works if I turn the power off and turn it back on, but only hashes for a couple hours.

I got a new SD card and flashed the image from the original SD and that worked for a few hours and then it stopped hashing.

I emailed tech support and they sent me an image that I flashed to the new SD card and the same issue.

This is frustrating! I know it works, I just dont understand why it keeps stopping.

No I am talking about 240 volts input. Much more efficient than 120 volts. the chips surely must be undervolted using 240.

Does anyone here run their S4's on 240 volts? What setting do you use on the chip? 0375?

Mining isn't my thing but judging by the stack of S3+ and S4 units that a friend has asked me to sell for him I assumed that the S5 was not too far off...

Ok so Bitmain has stopped single sales of S4's , only pallets of 16 left. And the current coupons expire on the 15th.  Maybe they are going to start sales of the S5 on Monday? 1Th  $375-400 750PSU needed is my guess. Any takers?