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Linked here is a video that will show you the steps required to replace any component of you Avalon 841. In reality their designs are so similar, that it is good for all models starting from the 721 series. Feel free to ignore the guy in the video calling it an 821 ::). The outer shell has an 821 label on it, and I didn't notice the difference until my final repair.

 Video  (https://youtu.be/KScUJ6gA-u8)

Thanks to Steven Mosher with Canaan for giving me the opportunity. It was simple I was sent an assembled unit that was non-functioning; and was tasked with identifying the issue and performing repairs. I was provided with an After Sales Support Engineer contact from Canaan, Yuxing Wei. I was able to update Yuxing on what I thought was the issue and how I was going to proceed; he also confirmed with me when I had completed the repairs.

Shipment Contents

• 1 - Avalon 841 Miner (https://canaan.io/product/avalonminer-841/)- non functioning (wrapped in an 821 outer shell)
• 1 - 1600W Sorcerer Power Supply (https://canaan.io/product/sorcerer-power-supply-unit/)
• 1 - Canaan controller (https://canaan.io/product/avalonminer-controller/) - This package includes 4 X Auc3 converters and 5 Micro USB cables
• 4 - Hashboards with thermal paste pre applied
• 2 - PMU boards - Due to the connections these are side specific, so be sure to identify the faulty board properly
• 1 - Control board
• Link to Troubleshooting and repair guide (https://canaan.io/wp-content/uploads/2018/05/Troubleshooting-and-repair-guide-for-AvalonMiner-models-721-741-761-821-and-841-release-v1.4-14.05.2018.pdf) by HagssFIN. Can also be found on the forum here (https://bitcointalk.org/index.php?topic=3224256.0)
  

*Will update post with screen shots *

First test - Getting a baseline for your issues I was able to log into the controller, and the unit was visible. Digging a little deeper into the API log it was apparent that none of the 4 hashboards were doing any work. There are a few different issues this could have been.

• 4 faulty hashboards
• A combination of faulty hashboards and faulty PMU's
• 2 faulty PMU's  - Despite them showing proper numbers for voltages, there can be an issue with the actual connections to the boards.

So I began as deep in as possible, and replaced all 4 hashboards and reassembled the Miner. I do have footage of this, but felt the published video was of better quality while still showing everything necessary.

Second test - How to identify if the problem is a Hashboard or PMU  
This test revealed forward progress. I now had 3 hashboards that were operational, with MW3 still appearing dead. I was left with 2 possibilities:

• The replacement hashboard was a dud
• There was an issue with the PMU2 - Attached to MW2 and MW3

To identify the problem board at this point, I swapped Hashboard positions. I removed Hashboard MW3, and MW0 and swapped them. These boards both sit at the top position of the miner but are each powered by separate PMU's. So I am taking a known functional board and switching it's position with the problem board.

Doing this allows me to see if the board is the problem or the board position. After the switch if the problem is the Hashboard, the API log would show MW0 as dead, and MW3 hashing. If the problem is PMU related you will still see MW3 showing dead, despite there being a different functional Hashboard in that position.

In my case the issue was an issue with PMU2. This was confirmed by MW3 still showing dead.

Third test

Armed with the knowledge that the Hashboards were all functional, I replaced PMU2. This was a fairly straightforward replacement, but it did surprise me. Using the API log I didn't notice anything that tiped me off to a faulty PMU as all my "VI" and "VO" number looked good. It was only through the previous Hashboard swap that I was able to confirm this issue. So it goes to show that you should not jusmp to conclusions and take your time in identifying the issue.

After swapping out the PMU, everything is functioning as expected.

Identifying Parts

When changing out the PMU units I noticed that one side is marked with an "L" and the other is marked with an "R"

https://i.imgur.com/tXo2C7Gt.jpg (https://imgur.com/tXo2C7G)

Reserved for edits and additions.

Edits
July 31 - Added screenshots, Typos and phrasing
August 10 - Added identifying PMU board and image

Nice job of troubleshooting.

Thanks,

If you don't mind I plan to link your post on voltage adjustments in the second post. I'm just waiting on a little more information so people aren't just blindly playing around with the settings.

Thanks for those tests by the way, otherwise I wouldn't be running mine at the moment.

They have helped a lot of people .

I have to say mine have run in the solar  array with air cooling and outside temps of 97f

They can survive the heat pretty well

Nice guide!!! The most important part people need to see is, Canaan's superior customer support. Not only are they providing
"in house" repairs, they are also implementing Repair Technician training abroad. This will cast a very big net of customer
support, and improve customer "downtime", by putting repair services closer to the customer's country of origin.


Kudos, to Canaan, and everyone involved in this helpful service!!!

Yeah the few days I was able to run everything so far the temps were hot, but with those voltage settings the machine kept chugging along.


Thanks I'm glad you like it. They really are a cut above the rest. Also if my video shows anything it's that they have built these machines in a way where anyone with the confidence and space can perform there own repairs

I cant help it, it was driving me crazy a few minutes into the video when you kept calling everything bolts when there isnt a single bolt on the unit.

https://monroeengineering.com/blog/bolts-vs-screws-whats-the-difference/

No worries, I'm amazed it hadn't been called out before. I actually considered getting rid of the audio as it bothered me; just a slip I hadn't realised until I was editing it.

In the end I just left it there as it still gets the point across.

I do all my you tube mining videos raw with no edits.

Many times I interchange cpu gpu psu while speaking on my gpu builds.

I have enjoyed seeing the inside of your garage many times ;)

I'm pretty sure I've seen most of them more than once. They've always been a great resource.

I think the raw footage was somewhere around 50 minutes. Luckily most of the rambling was during the repetitive screw removal sections.

I meant it in fun, I should have probably added that the overall content of the video is quite good, thank you for making it!

If looking for studio-quality editing I highly recommend Sony Vegas Movie Studio HD Platinum. You can often find the not-latest versions for around $100. Phenomenal program that does all you could ever want.

No offence taken, glad you liked it.


Thanks. I think I'm going to try and keep it fairly straightforward. I know I barely tapped the features available for this video, I might play around with it in my downtime just to see if I can enhance the troubleshooting visually.