R4 board PCI connectors melted

[powrslave]

I have an R4 and 3 PCI connectors melted into the power ports.

Would it be worthwhile to send to Bitmain, solder myself, or look for someone in the USA to do it cheap?

If you know of any services in usa familiar I'd like to know.

[philipma1957]

I have and R4 and 3 PCI connectors melted into the power ports.

Would it be worthwhile to send to Bitmain, solder myself, or look for someone in the USA to do it cheap?

If you know of any services in usa familiar I'd like to know.

forget bitmain.

maybe hmtech  can repair it.

https://hmtech.co/

they helped me with a whatminer m20s

they are USA based.

[HagssFIN]

User "lightfoot" from this forum replaced burned 6-pin connectors in my BW-L21 miner back when I had it, and he did a great job.

He is USA based.

https://bitcointalk.org/index.php?action=profile;u=148567

[lightfoot]

Yep, I have done a *lot* of those power plug repairs in the day. It's a combination of cheaper plugs on the part of the manufacturers and using power supplies that sag voltage under load (leading to higher amps at the plug which leads to more heat, etc). Then things just turn to a messy goop.

The trick to replacing them is pre-heating as they are directly tied into the power planes on the board which just wick away any heat applied from a normal soldering iron/heat gun. Bring the board up to temp, then a good iron can be used to loosen the pins without worrying about damaging any of the traces on the board or pulling out the via.

Make sure you flux the pins on the new plugs with something like zephlux before putting them in, always clean out the holes completely and don't force the new pins in, and of course spend the extra buck and get nickel PCIe plugs instead of the normal tin/brass ones. Nickel ones work a lot better....

[NotFuzzyWarm]

Should add that another reason for PCIe power plugs melting is folks using the same PSU's to power a few consecutive generations of miners. The connector socket pins are rated for surprisingly few mate/unmate cycles before the plating is scraped off so repeated plugging/unplugging of the connectors is very bad. Lose the plating > higher resistance > more heating > remaining tin plating begins to oxidize and eventually things avalanche to failure. So to be on the safe side, if the PCIe connectors on the PSU have seen a lot of use - then re-pin them.

Oh, and how few cycles you ask? I've seen manufacturer ratings for mating lifetimes as short as 10 cycles for el-cheapo socket pins. One does have to remember that these connectors were designed to be very seldomly plugged/unplugged as most of the time the connections are made only once in the lifetime of normal computer equipment.

[VRobb]

To add to NotFuzzy's point, I use a touch of conductive grease when I first plug in the connectors to help with both wear and resistance.

[Artemis3]

I have an R4 and 3 PCI connectors melted into the power ports.

Would it be worthwhile to send to Bitmain, solder myself, or look for someone in the USA to do it cheap?

If you know of any services in usa familiar I'd like to know.

I have an acquaintance that suffered the same, and he soldered himself. For Bitmain the R4 is no more, i don't know what would happen if you ship it to them, but maybe the American branch could repair it, no idea.

NotFuzzyWarm might be into something, as i have never unplugged those from my R4 for the last couple of years and its doing fine.

[lightfoot]

Board came in today and I'm taking a look at it. New plugs are on order (as I said I like using nickel plugs instead of brass) but in the meantime I thought it would be neat to post some pictures. I'll ultimately add this to a new thread on R4 repair* but unless people don't want me to I'll also post a few pics here.

The board itself:

https://i.imgur.com/tHh64Tj.jpg

R4 boards are interesting. 64 chips, a choke, and the pic circuitry. Nothing complex, but a very long board so the air can roll across it without all the resistance of a normal S9 board. You can also see some of the heat sinks are slightly mis-aligned, but worse things have happened....

https://i.imgur.com/HSsSJOl.jpg

Close up of the end of the board: All three plugs are badly burned. Also oddly enough it's the bottom pins that melt first, which is *very* bad. That's the ground pin, and if all of them open the board will suddenly have +12 and no ground. At which point the electricity will seek a ground and will find it in the signal cable. Which will then burn open, damaging the board's circuitry and possibly the controller. Yuck. You can also run into the situation where the ground vias are burned to the point that there is no conductivity, in which case one has to build a new ground plane. Do-able but a real pain in the rear.

https://i.imgur.com/JKr2Yr7.jpg

Top view, close up where you can see the heat damage to the circuitry on the end. This pin set was really getting hot, the bubbled plastic tells how warm everything got. Check your plugs: If they feel warm then they are too hot and you need to either slow down your miner or get a better power supply.

I'll pull the old plugs this weekend. OP did this board still hash or did it shut down? What's the other board look like, and were they all on the same power supply?

[powrslave]

OP did this board still hash or did it shut down? What's the other board look like, and were they all on the same power supply?

This board shut down and the other kept going fine.
They were on same psu DPS-1200FB-1 A

[lightfoot]

Hm. Wonder why the second and third pictures aren't showing up. Anyway took the bad plugs off this evening and cleaned up the board. One of them burned right through the connector and into the board. Fortunately there isn't a ground plane short, so I'll clean it all up tomorrow and wait till the parts come early next week.



The plugs off the board. Typical mess, what happens is when one pin fails the rest of them have to carry the full load. As more fail, the remainder get hotter and hotter. My guess is the center one on the really burned plug was the "last to go...."



The board after removal. The top pad is warped a bit from the plug burning out, but as I mentioned there is no ground fault so it should be ok.

Next up: Putting shiny new plugs on, next week.

* Note: My personal philosophy is that information should be free, but skills should be paid for. That's why I like to write up and take pictures of this stuff, other people should be able to do it, and if they do they should charge based on their skills, not on hidden sequestered knowledge.

Just wish mining companies did it as well, reverse engineering some of this is a real pain :-)

[lightfoot]

All done! Got the parts today and put them on the board.



For getting the solder out of the holes start with a solder sucker, then use solder wick to get all the old solder out. Not only is it neat but it protects the vias from being damaged by forcing pins into the holes. I have found that putting some flux on the solder wick will allow it to really suck up all of the old solder and make a neat hole.



Then put some flux on the pins of the plug before inserting it.

Heat up the board with the pre-heater, then solder the pins. You should never have balls on the pins, the solder must flow completely into the hole to make a good strong connection.



Then it's off to test it on the bench. I don't have an R4 code load, but an S9 one works well enough.



Board pulls a good 300 watts under load.



And is hashing test nonces.

Time to box it up and send it on its way. Hope this write-up helps other people if they decide to do it. But if you need someone to do it drop me a line.

[powrslave]

And we're back 
Great job thank you lightfoot

chain#8