S17 Pro Back from Repairs or Disrepair.

[wndsnb]

Did you order from the store from my link, CN888 Store? I successfully ordered 5 times without issue from them. I've also ordered from here too.

Not sure a stereo microscope will be all that useful. I have a Bausch and Lomb on a boom stand, similar to this, but I don't use it for hashboards. Good for inspection after rework, but being fixed in a vertical position isn't ideal for placing/moving components when reflowing.

So far, what I've ended up using most is something similar to these: https://www.magnifier.com/headband-magnifier-eye-glass-style-5-lens-led-eg1li.htm

If I was going to drop >$500 on something, I'd go for some decent surgical loupes rather than a stereo microscope.

[mikeywith]

... on the search to find a reliable source for BM1397AD's.

Did you check on zeusbtc.com? I think most suppliers are facing chips shortage, it seems like thousands of gears were sitting on the sideline doing nothing until BTC took off and everyone wanted to fix those gears, I think you can actually extract the chips from one of the boards you have, say you have 10 bad boards, you sacrifice 1 to fix the other 9, makes any senes?

if this works, it will add an extra step or two on the process, but at least you don't have to wait forever to find the chips.

[wndsnb]

I've also ordered successfully from Zuesbtc. It's a bit of a process though to get an order in through whatsapp.

I ordered 100 1397AI chips from IOTstore on aliexpress on Sunday and they have already shipped and are due to arrive on Friday.

[NoKeyboard-BTW]

I did order from the CN888 store, they were responsive to why it was cancelled (said it got lost) but seemed off. Might give them another go since it looks like you have recently been successful or the IOT store. ZuesBTC is was the plan B and wanted to get some feedback on them before going in that direction, so thank you for that mikeywith, and the cannibalization of other boards approach.   Surgical loupes seem like a good idea but this PIC chip work and booster might need the microscope to make sure contacts aren't bridged - if they are, be able to correct them properly.  What miner do the AI chips go to? Just looked at the IOT store and just got more confused. This 53 pro came with AD's. They have AH, AI, and AG, is one better than the other?

[wndsnb]

If you do go for a stereo microscope, a nikon with a 0.5x auxiliary objective gets you ~180mm working distance. Mag with the 0.5X should be more than enough, and the extra working distance is key if you want to try to use a hot air tool. You can find some pretty decent deals on ebay for a nikon on a boom stand.

I have pretty good vision, but I still think it's overkill. I'd recommend spending the $20 on some cheap 3.5X magnifying glasses like I posted a link to before and give them a try first.

I don't have an official answer on the difference between AD, AG, AH, AI... but according to Zeus they are all interchangeable. I've used the AI successfully for S17, S17 Pro, T17, and S17+.

From the Zeus website:

[NoKeyboard-BTW]

You're right, not any info about these variants online.

[NoKeyboard-BTW]

Wndsnb, I wanted to circle back on this because I was reading one of your replies in an old thread about repairs on the S17. My question is if the copper film is completely off (lets say from a heatsink coming off) what is the reason you can't solder it back onto the copper-less chip? Is it from the degraded thermal transfer? Also, since as of today chips seem to have disappeared from Aliexpress (I did get some several weeks ago) - What is your procedure for taking a chip from a dead board and implanting it on the working board - keeping this copper film in mind. Also, as an update, the equipment is slowly coming together. I can't help but think that self-repair will be the norm for these machines. You're light years ahead of this. Still haven't found any info on chip bm1397 chip naming convention differences.

[wndsnb]

The purpose of the copper plating is to accept the solder, without it the solder won't flow. Think of water on a hydrophobic surface (like a windshield treated with rainx). So you could probably attach a heatsink with solder, but it would not make good contact because the solder will not flow over the whole surface of the chip. You could attach a heatsink using a thermally conductive adhesive, but that has other issues, like how to remove the heatsink if there is an issue with the chip or its connections.  So I always replace chips that have lost their copper plating.

I haven't done a lot of swapping chips between boards, most of the time I'm not going to take the risk of installing a chip that may be faulty. Just not worth the cost of a new chip to spend the time of putting it on only to have to remove it and reinstall another one. But the only advice I have for that is that you should either clean the solder off the chip or the board. If there are solder bumps on the chip and the board, it is very difficult to get the chip aligned, and when you heat it up it will shift. So I'd probably leave the solder on the chip and use solder wick to clean the solder off the board.

Workbench update...

I added a benchtop DMM to my workbench a few weeks ago ... I'm loving it so far. Don't really need the accuracy, but the time to make measurements is way less than the portable I was using and that time adds up.

Also pick up a Hakko FX951 soldering iron. It works great, but I'm now curious about a Thermaltronics iron (which is basically Metcal clone, started by previous Metcal employees).



Looks like AD and AG chips are all gone, but AI chips are still available, https://www.aliexpress.com/item/4000098330595.html?spm=a2g0s.9042311.0.0.d9754c4d7ET3MD

[NoKeyboard-BTW]

It's such a great set up and I like the new addition of the desktop DMM to save you a few minutes here and there. One more unit and you might have to hire a real estate agent. Nice catch on IOT. They seem to be the go-to with good communication and delivery. Not surprisingly, they said prices will be going up so I grabbed a handful of AI's. The Hakko's do the job at a reasonable price (using an FX888) until I can find a used JBC Nano or desoldering station. I did pick up a used Zeiss SM and used JBC hot air station recently.

Thank you for the clear explanation on the copper. It's saved me a lot of future headaches and seems to be the rule of thumb that if a heat sink does come off it'd be best practice to replace the chip because you'll have to wick the old solder bumps off and the copper will come with it.  Adhesive just isn't a good option long term. The more I think about chip swapping and from your approach, the worse it sounds vs. just replacing it with a new $8 chip.

Thanks again for sharing your experiences as a lot of us start to navigate this and sharing your incredible station. It's super helpful.     

[wndsnb]

I have seen a few heatsinks come loose without taking the copper plating with it, but for the most part I'd say the main reason why the heatsinks come off is because the copper plating delaminated. The delamination is a manufacturing defect, you can clean solder off without taking the plating off if the chip is not defective. This is what chips with delaminated plating look like:



Sometimes the heatsink was never attached very well, and the solder will just break off, or the chip got hot enough that the solder melted. So in those cases, the solder will still be on the chip, and you can clean it up and re-attach the heatsink with no issue. I also don't generally remove all the solder on the chip, I just add a glob of flux and reflow the solder with a soldering iron (with a good-sized chisel tip) so it is smooth and covers the whole chip. If some or all of the copper plating is gone, then the solder will just bubble up and it will be impossible to get it to flow over the whole surface of the chip.

[NoKeyboard-BTW]

I see, the copper delaminated from one of the chips with the dislodged heat sink and will have to be replaced. I've concluded this copper film and the solder is well below sub-par as you suggest after working with it. Thank you for the insight/method of reflowing the chip with the factory solder on the chip with the chisel tip. I wonder if it's also sometimes necessary to add a little solder paste to replace the solder lost on the bottom of the dislodged heat sink. It would be great to see a picture of your perfect reflow on a chip for reference.


I do have 3 dissimilar questions I hope you could shed some light on:

1. If not running Bitmain stock firmware would you ever need the EEPROM flashing option that ARC offers?

2. I know you touched one this earlier but does the Bitmain repair center detect other issues like bad PIC chips and temp sensor errors? To what level does ARC do this?

3. After taking the bad chip off I noticed on one of ARC's videos that they didn't use a tin and new solder paste to put the new chip in. (that I sometimes see in videos). They added some flux and re-heated the old solder there?

https://www.youtube.com/watch?v=SE-YJRTZezk

Edit: If I go with ARC I will ask them about the editing of those EEPROM values. So it might be a good option to add. 

[wndsnb]

Nope, no need to program the eeprom unless using stock firmware.

It will detect and read temp sensors.

If the pic is bad, nothing will work, so there isn't really anything to detect.

As far as how to replace chips, there is no correct answer. But I no longer tin the chips with a stencil. I was never able to reliably get a chip on that way and had to drag reflow the connections with an iron, or add solder paste and clean up after. So I started just adding some solder to the main power pads and not bothering with any solder on the pins. I leave solder on the PCB, and then add flux and drag-reflow the pins with an iron after flowing with a hot-air tool.

Every set of tools and every person's skills are different though, so you really just need to try different approaches and figure out what works the best for you and the tools you have.

[NoKeyboard-BTW]

I was able to take a closer look at the PIC chip under microscope and seems that when the temperature sensor was replaced and reflowed it dislodged half of the pads on one side. So that half is just floating in the air. I'm gonna take a wild guess and say that is where no PIC detected comes in.

For the other board, the chip with the fallen heat sink is going to be replaced but I am seeing conflicting information on what solder paste to use for chip replacement. I'm seeing some use 180deg. paste?

For the heatsink replacement: Amtech 138deg. low temp. SN42/Bi57.6/Ag0.4 Lead-free. And the Chip Quik you reccomended.
 
Solder wire: Kester "44" SN96/AG03/Cu.5 Lead-free.

For the chips: I'm confused here on what to use.

Could you recommend the best formula of paste solder and temp. for replacing chips? Do you know what temp. paste it is from the factory?

Would really appreciate your opinion on what solder I'm currently using and a direction for the chip paste.  

Thanks again. 

[wndsnb]

Yeah ... pretty sure the chances of working with half the leads disconnected is pretty low... lol.

I use the same chipquick for the chips as well. Don't know what they use in the factory, but I think in some of the Bitmain repair manuals it mentions low temp (138DegC) for everything. I like using it because you can keep the temperatures lower so less chance of destroying a board. Although it does make putting heat sinks on a bit tricky, would be easier if the chips were attached with higher melting point solder.

[NoKeyboard-BTW]

Thanks for the temp. confirmation. Ha. That PIC chip. It amazes me how many things can go wrong with these and you really have to double-check your work. 

The higher temp. approach is interesting and since the factory solder is so weak I think of a higher temp Sn/Ag solder paste to improve strength. At a cost.

[wndsnb]

I'm not sure solder melting point is the issue with the original assembly. I'd guess either poor temperature profile or just faulty/expired solder paste. Many of the chips I remove show signs on the large pads that the solder never flowed enough.

[mikeywith]

What miner do the AI chips go to? Just looked at the IOT store and just got more confused. This 53 pro came with AD's. They have AH, AI, and AG, is one better than the other?

As mentioned by wndsnb, they are interchangeable, but according to Zeusbtc you want to avoid using more than 4-5 of different chips on the same hash board, so if you can't find 1397AD for your S17 pro, you can get the AH,AI or AG version, but having more than 4-5 of them alongside the AD's will create issues and the hashboard might not function properly.

[NoKeyboard-BTW]

Thanks Mikeywith, I saw that too and I think not going over this and avoiding this arrangement is the plan and wait for the AD's to become available. Wndsnb, I removed one of the chips and two of the smallest resistors (they had a black top with white core) blew off - one was labeled R2020 and the one next to it was a R2016. These are right next to the chip. I would assume that the R2016 is 201MΩ ± 1% and the R2020 is 202Ω ± 1%. Do you have any direction on how to find these on Mouser? Or do you have another source? Oh, and apparently I don't have the micro tweezers for this job what are you using for these things?

Edit: Looked on ZuesBTC to see if I could narrow it down but didn't find anyhting. Also nearby noticed C86 and C84 (ceramic capacitors?) were off so if you have leads on these types it would be appreciated.

Thanks again.

[wndsnb]

Those are most likely 33ohm resistors. If not, they are 0 ohm. What leads on the asic do they connect to?



I'm pretty sure the ones I circled are 0201 resistors, ridiculously small ... like grain of sand small. It is defiantly a pain in the ass to get these on, you need some good tweezers.

https://www.digikey.com/en/products/detail/panasonic-electronic-components/ERJ-1GNJ330C/8343545

https://www.digikey.com/en/products/detail/panasonic-electronic-components/ERJ-1GN0R00C/3982319

The caps are either 1uf or 0.1uf. I think they are 0402 size. These should work.

https://www.digikey.com/en/products/detail/kemet/C0402C104K4RACTU/789653

https://www.digikey.com/en/products/detail/cal-chip-electronics-inc/GMC04X7R105M6R3NT/13908742

[NoKeyboard-BTW]

These are on the imperceptible scale until you put them under the scope.  I had a heat shield surrounding the chip to protect against just this and bumped it - this is the result. I circled the ones missing in red and seem to match the ones you have circled. To confirm, these are 33ohms? I see there is a mix of 16v and 6.3v and .1uf and 1uf I am having referencing your image these are arranged differently than mine. I'm guessing the C86 and C84 are 1uf 6.3v each.  Always, fantastic again helping narrow this down.

https://drive.google.com/file/d/1dTTemJ5p_tO1IKapT-JEEDsAXIpJRPOm/view?usp=sharing