Cheap and simple repair of S7 hash board

[tubexc]

S5 are unregulated; since this is a repair for the regulator it can't be applied to S5.

Thanks for quick answer sidehack ! 
Do you know any fix for not working antminer s5 hashing boards without any apparently burnt components ?

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[tubexc]

On this page ( https://bitcointalk.org/index.php?topic=1199534.20 ) i see a few attempts with the Low-dropout regulator but I do not know if it works.

[lightfoot]

Photos are a page or two back, they're actually pretty good and show where to solder the wires for the pot repair.

Question: Does anyone know the part number for the U2 component? Tried to look up the numbers (AG1V) but didn't find it easily. I've got a few boards here and it would be easier for me to just replace that component than stick pots on the side :-)

(Edit: Is it just a H11AG1VM optoisolator? Interesting choice of part if so....)

C

[lightfoot]

This is fun. I'm working on a pair of R7 boards that are down, tried a 50k PCB variable resistor between R17-U2 and ground, no dice.

So I started checking things. The voltage on a good board at the choke with the board plugged into a PS and no controller is about 8.5 volts. So there is a stock setting. One the two bad boards, the voltage is a solid 0.0 volts.

Checking resistance on a disconnected board I see about 18.4k at R17-U2 and ground on a good and bad board. Thus I think the variable resistor is ok.

Checking resistance on the choke to ground shows a resistance cold of about 30 ohms, so the chips are good.

Checking resistance on the +12 to ground I see the 1k and up reading as the caps charge, so that's good.

Checking the FETs I see the gates are not shorted to ground, source and drain go to ground normally. It's *possible* the low side FETs are shorted, can't tell yet (If they were, the controller chip would shut down the high side FET when it saw the cut-through current go way up).

So it looks like the buck regulator here is bad. Either it's the controller chip, or the low side FETs. Interesting.

Next up: test the low side FETs manually. If they're good I think I have a dead power converter chip. Not too bad to replace, but man I hate QFN packaging...

C

[lightfoot]

Interesting. The 27402 buck controller is pretty dirt-simple, feeding a 60a low side FET and a pair of 60a high side FETs. Given the voltage differential is minimal they can get away with this using 60a FETs on the low side with a fast switch cycle of ground. Clever. Still I wonder why it's not coming up at all...

If this is what Antminer uses on the S9's then these are really simple to troubleshoot and fix. Hm....

[hoschi]

Hello everyone,

I have a S7 with 45 chips...
Board one only detects 23 chips...but sometimes it detects all 45 chips..
Once (1 from 100) it runs perfectly with all the 45 chips
Even if it's dectects 23 chips it runs only stable for couple of minutes..is there any chance to repair it?

Is this Picture https://4.bp.blogspot.com/-GOoFIu8c82s/V18K4PYcePI/AAAAAAAGi6I/BOOf0PaRMkoezoFTYsaj1cJOeUiurgq8QCLcB/s1600/antS7-top-view.jpg correct?
So my faulty board (one) would be on the left side?

Thank you

[lightfoot]

Hello everyone,

I have a S7 with 45 chips...
Board one only detects 23 chips...but sometimes it detects all 45 chips..
Once (1 from 100) it runs perfectly with all the 45 chips
Even if it's dectects 23 chips it runs only stable for couple of minutes..is there any chance to repair it?

Is this Picture https://4.bp.blogspot.com/-GOoFIu8c82s/V18K4PYcePI/AAAAAAAGi6I/BOOf0PaRMkoezoFTYsaj1cJOeUiurgq8QCLcB/s1600/antS7-top-view.jpg correct?
So my faulty board (one) would be on the left side?

Thank you

Hm. What is the voltage as measured between ground and the inductor?

C

[hoschi]

LOOOL
Apparently it was too cold in the Garage (10°C)...
I took it in the house and it worked perfect with the same PSU.
So I swap board 1 with board 2 --> garage --> same Problem only 23 chips detected.
So I change the freq an it reboots the "miner" --> all chips are there....
Now it's running stable over 16 hours  .

Next time I'll messure the voltage between ground and the inductor (inductor has usualy 2 connectors right? which one should I take)?

Regards
Armand

[lightfoot]

Either one would be fine, there is far less than a 1 ohm difference on the inductor.

That said, if you want to freeze a miner *then* check the voltage that could be a neat data point. I've been split on the cold temp not starting thing; either it's a temp sensor on the DC-DC converter flagging low and keeping the osc from firing, or it's a chip that loses connection with the board when cold. If there is no voltage on a board when cold but voltage when warm we have identified the problem that kills R4's and S7's and probably S9's.

Neat, hm?

[hoschi]

DAMN....it worked only for about 2 days ...

I'll check the voltage....

[lightfoot]

Hm. When did it fail, how did you know, and was there any error messages or beeping to note?

C

[hoschi]

I saw on antpool, that the S7 only hashes with about 3,1 GH/s.
There was no beeping...
The voltage between the inductor and ground is 10,75 V.
Input Voltage is 12,13 V.

Regards
A.Tarjono

[lightfoot]

Interesting. DC-DC converters are fine, so it's got to be the crystal. I have a board like that here, I'll try swapping the crystal and see what happens.

C

[hoschi]

Sorry for asking but what is the crystal?

Please let me know, if it works...

[lightfoot]

Sorry for asking but what is the crystal?

Please let me know, if it works...

It's the 25mhz crystal that is just barely under one of the heat sinks north of the coil. That I believe is what provides the master xclock to the chips; they put in a whole bunch of pads for secondary clocks but I think they drive each chip's clock from the previous one in a line. No clock=no chip running.

There's usually 3 things each miner needs:
Power
Clock
Signal

Get those three and working chips and you should be underway in some capacity. We have power, next thing to check is clock.

Oddly enough I wonder if sub-standard crystal chips are the cause of low temp failures. They should run down below 0c, but maybe they don't.

C

[guy_fox]

I have a faulty S7 card, and I've often suspected a faulty crystal.

At it would sometimes hash at higher frequencies, but not lower.. and would run a day then errors would start increasing and it would stop.

Please can you post a picture of the crystal, I've tried to cross-reference the numbers online, and none seem to match a crystal.

[lightfoot]

I have a faulty S7 card, and I've often suspected a faulty crystal.

At it would sometimes hash at higher frequencies, but not lower.. and would run a day then errors would start increasing and it would stop.

Please can you post a picture of the crystal, I've tried to cross-reference the numbers online, and none seem to match a crystal.

Hm. Sort of works. On this board I'm testing I now can hash at 125mhz, but it says only 21 chips are there. Which might mean the crystal/oscillator I'm using doesn't have enough power to run the string.

It's the little silver thing with 25.00 on it between two chips right above the inductor. Can't miss it. Getting it off without knocking off a heat sink is an exercise, but I have something that does work here (albeit slowly).

So I might need one that takes a different input voltage or can drive more stuff. There are several crystal pads on the board, but only one is used. Hm......

[Stivix]

Hello,

I have only two "O" on one hashing board.
There is no other "O" or "X" visible on this board.
Do You know 50k potentiometer will work in this case?
https://imageshack.com/a/img923/7604/R6IfkG.png

I have tried to reduce the frequency but the problem was still occurred.

[lightfoot]

Check the voltage when the unit is up and running from ground to one of the ends of the choke coil. If you see about 10.6v then the power supplies are good. If not then the chip may be out.

Need to see if there is an exact replacement for this oscillator; the ones I am swapping in might not put out enough power to run the chips. Hm....

[Stivix]

Can You describe what choke coil do You mean?
Can You provide some photo of the choke coil? 

Is there some possibility to check it without disassembling the miner?