Cheap and simple repair of S7 hash board

[Stivix]

Hello,

I have just disassembled the miner.
The voltage between coil and ground was:
10,5V on left side of coil when You look from fan side of the miner.
9,5 V on right side of coil.

The voltages are similar than other two hashboards (10,6V and 9,5V).

I have checked to crosscheck with other hashboard, to check if the problem is caused by controlboard or cables, but it looks there is problem on the hashboard.
The chips are cold during startup and on two next hashboards chips are hot at startup.

I think the chips have not power to startup...
What I saw TF LED not flash and on next two working boards it is flashing all the time.

Has somebody similar problem?
Do I have to solder 50k potentiometer?
Can somebody to sent the photo from first message of the topic because links not works right now?

Edited: I have soldered potentiometer but U2 was still on the board.
It was not helpful...

Next test - I have unsoldered U2 but there was no positive result.
Miner has to run with potentiometer 50k - it works.
I have still two "O" visible on one hashing board.
There is no other "O" or "X" visible on this board.
Total speed is 3.2 Thash/s.

Any person can help me in this case to speedup the miner??

[cableiso]

I am looking at a couple of S7 boards with a few dead chips.  Many upstream chips look good, but I'm having trouble communicating with them to verify.

Does anyone know if the BM1385 CRC5 is the same as the BM1384 CRC5?  Meaning 84 00 00 11 is a complete getstatus command..

I was considering pulling the whole tier of chips and undervolting ala this thread to compensate, but I *believe* that the ribbon cable's TX is non-level shifted, while the CI at the input side of each tier IS level shifted.  Meaning it won't talk unless I negatively level shift the ribbon's TX, which I'm not thrilled about doing.

I am currently considering pulling one tier + one chip of the next tier to access a non-level-shifted CI and strapping in a diode or a flipped-over 1385 to take up the extra current, but that's major surgery.  Best to make sure I'm sending the right command before pulling 4 chips and getting my splice on, heh.

[lightfoot]

Hm. If you brought the voltage to 11.5, why not just short the +12 pad next to the choke to the choke and just run the chips on straight 12v?

[EVCX1]

Hello, this is my first post here, I found this thread about 4 days ago.  Recently, I had my S7 fail and I was getting 9.2v on the coil leads. I performed the 50k pot insertion and removed U2.  I can now adjust the voltage to 10.6 or 10.7 but still I see 48 Asics and 0 hashing going on.
  
Before I modify board number two which has 8.2v at the coil which I read in this thread may be a PIC problem, would I do the 50k pot insertion and then pull U2 and the PIC or do I need to try and replace the PIC?  If so, how does one get a new PIC for this?

[guy_fox]

So I removed crystal from my non-operational S7 board as I suspect this is the issue.

Removing it is a bitch, and I damaged one of the pads and accidentally removed the crystal capacitors and resistor.

The query I have is with regards to the replacement of the crystal:

1.) I see there are numerous pads for crystals, and only one is used.

However, on all the others, pin one of the crystal is connected to the CLK pin on the test point, but this is not the case on the one used. Anyone know why?

2.) Can I install a crystal on any of the pads (there are a few that are allot more accessible than the one used)

3.) I hooked up an oscilloscope to measure the 25MHz clock and it seems to +3V DV, can anyone confirm that this is the crystal voltage?

4.) None of the crystal data sheets indicate operational voltage, is anyone here more familiar with that?

Thanks

[ruinous]

Very green and don't know much about PCB layouts or components when talking about coils and such.

I feel one of boards is suffering from low voltage after a read through the eight pages here (possibly a second is starting to fail as well).

Where exactly do I measure the voltage on the hash board? Please feel free to speak to me like you would a child as this isn't very far from how I feel anyway after prodding around the board with the multimeter

[lightfoot]

Sure. You can measure the voltage on either of the two choke pins. The choke is the big red thing that looks like a cross between a magnet and a donut, 2 solid wires coming out of it into the board. Below the power plugs, can't miss it.

Meantime, been working on a few boards that won't come up. Running the board with no controller attached does pull current, and with an appropriate IR camera you can see some things after awhile. For example:



As you can see, one of the chips is not like the others. Being that it's hotter, it is probably shorted. And being shorted it's not passing control signals and whatnot. So off it comes, to be replaced by another chip....

This seems to happen a fair bit. And it's fun to roll out the bigger tools, kind of makes me feel like a Predator or something......

[ruinous]

Thanks I got a read, I was using AC not DC settings

Card in question is 10.7v with 30 asics displaying "-" 's and goes to "o" 's after a while but no hashing. frequency at 700 read at 10.7v. So Imagine the fix outlined in this thread isn't what I need after all?

[lightfoot]

No, different problem. At this point it seems to be either a shot crystal or a shot chip. I can identify the shot chips, working on better ways to swap them out (not difficult, just time consuming)

[fanatic26]

No, different problem. At this point it seems to be either a shot crystal or a shot chip. I can identify the shot chips, working on better ways to swap them out (not difficult, just time consuming)

I found replacing the chips to be the single hardest part about doing the repairs. I guess I just need a steadier hand.

[lightfoot]

I found replacing the chips to be the single hardest part about doing the repairs. I guess I just need a steadier hand.

They're easier than QFN, the side power rails really help them to self-center on the pads. However did you find the bad chips using thermal imaging or something else?

And did you use air or a soldering iron?

[ruinous]

I don't have equipment outside of basic tools for small repairs, I have a IR pen but I imagine it will take a lot longer to find a bad heat signature then with a camera. I started a thread for repair service in US. Maybe I'll get some good recommendations as a second board decided to go down now.

[fanatic26]

They're easier than QFN, the side power rails really help them to self-center on the pads. However did you find the bad chips using thermal imaging or something else?

And did you use air or a soldering iron?

I found the bad chips by doing hardware diagnostics on the board. There are two heartbeat signals on the board, one going beginning to end, the other end to beginning. By using the test points on the board you can isolate the issue down to the individual chain of 3 chips. From there you can do some resistance testing and figure out which chip is shorting.

I used a heat gun and tweezers for all removal and replacement. That is how the bitmain techs do to work on the boards.

Heat em up, pull em off, tin the new chip, and drop it into place.

[rfsimoes]

Hi all,

Has anyone found were the temperature circuit is at?

Thanks in advance

[ShefSam]

Hi all,

Has anyone found were the temperature circuit is at?

Thanks in advance

EXCELLENT QUESTION!  Been wondering/trying to isolate for months!!!

[ShefSam]

Is there a definitive explanation for why hashrate will degrigdate from perfect/normal (or at least acceptable) when fans are fine, temp is fine, no chip errors, default or reasonable frequency is set, etc. et al...? Unit seems and reads perfectly fine, but cannot hold its hashrate.

Please advise.  Any way to remedy?

[lightfoot]

Hi all,

Has anyone found were the temperature circuit is at?

Thanks in advance

Not sure if there is one. I think the software reads the temps on the chips and reports the high chip or something.

[Sweminer777]

do we have more deep info about s7 boards? overclock underclock repair and part spares ?

[lightfoot]

do we have more deep info about s7 boards? overclock underclock repair and part spares ?

Well, sort of, but if I might ask, why? Are S7's now profitable, if so I have one in the junk pile here I should fire up or sell. S9's are, and of course Titans are very profitable but S7's?

[Sweminer777]

do we have more deep info about s7 boards? overclock underclock repair and part spares ?

Well, sort of, but if I might ask, why? Are S7's now profitable, if so I have one in the junk pile here I should fire up or sell. S9's are, and of course Titans are very profitable but S7's?

well machines always profit on free electricity ? but  i was thinking more like Voltage and electricity mods to get them more efficient.