[Solved] Corrosion on cables from heatbed  

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danielsillar
(@danielsillar)
New Member

I was having some problems with the heatbed and upon checking the Einsy board found the Heatbed-Einsy power cable had corroded, and the corrosion had spread to the PSU-Eisny power cables as well. 

I figure i need to get a new Einsy board: https://shop.prusa3d.com/en/mk3mk3s/197-einsy-rambo-mk3.html

And some new Heatbed-Einsy cables: https://shop.prusa3d.com/en/mk3mk3s/694-heatbed-einsy-power-cable-screw-attached.html

But im not sure about the PSU-Einsy power cables as the ones in the shop ( https://shop.prusa3d.com/en/mk3mk3s/970-psu-einsy-power-cable.html ) say they are only compatible with the black housing PSU while i have a silver housing PSU. Will i need to buy a new PSU or is there some alternative cables I can use? Any help would be appreciated.

Best Answer by morphias:

I'm an electrician.

You are very lucky not to have had a fire!

You have a few issues there. As @andrewld said, it 'looks' like the terminals were overtightended given how off center they are.

Alternately, given all the burning and melting, they may not have been tightened enough and that has lead to 'hot joints'. A hot joint is where an electrical connection has insufficient surfance area conact for the current to flow. This reduced surface area means the same amount of current is still trying to get through, but can't. This causes heat due to the 'resistance' or 'opposition' of flow.

Think of it like a hose with a kink in it. The water pressure is still there trying to force it's way through. What ultimately happens is the hose bursts or blows the connector off back at the tap.

There isn't any acid in solder rosin (flux) unless you specifically purchase acid flux solder. Electronics manufacturers definitely do not use this stuff.

The board and PSU are likely salvageable if there are still functioning. They will need to be removed and VERY cafefully (so as not to damage any components) cleaned up. A soft bristle toothbush will help and a can of compressed air and electrical components cleaner. Your local 'Radio Shack' style store (Jaycar or Altronics in Australia) or electrical wholesaler will have it. I will say this again, VERY CAREFULLY! You are not scrubbing rust off a piece of steel with a wire brush. 🙂

Something like this: https://crcindustries.com.au/products/crc-co-contact-cleaner-350g-2016.html

The cable compatability will simply be the length of the cables given the different route they take with the different models of PSU.

As @andrewld said, get new cables made from high temp silicone insulated wire of no less than the current gauge. Bigger is better, but definitely not smaller or you will get into the hot joint issue again.

It does look like you may need a new power panic cable, but it's hard to tell from the pics.

You need to support the crimp terminals when you tighten them. Don't let them twist into the plastic separators and leverage against them. They are not deisgned for that. They are there as electrical separators to prevent dead shorts.

After everything is reassembled, you could give the terminals a spray with an electronics preservative to stop the air getting to the copper in the cables. Not sure where you live, but salty air can cause the patina (the green 'growth) you can see. This also causes hot joints.

https://crcindustries.com.au/products/crc-2-26-electrical-multi-purpose-450g-2005.html

 

For the record, I have no affiliation with CRC Industries - they just make excellent products and I use them daily in the course of my job - a lot of which is maintaining, repairing, designing and building industrial control systems.

 

Ben.

Posted : 19/06/2020 7:45 am
Andrew
(@andrewld)
Estimable Member

The corrosion looks like an acid attack from the melting plastic or flux from a solder joint.

But as for cables, get heat resistant flex from a hardware store. Better yet go to one of the charity shops and buy an old iron. So long as the wire is no less than the diameter of the one in use you will be fine. I suspect the "suitability" comment is more to do with the cut length than the cable type.

I note also that the connectors are off the true. This suggests they were horsed up super tight. Tight is good but too tight risks breaking the connections at the board. 

If making good crimped connections worries you get a trustworthy electrician to make off the ends for you.

Hope that helps.

Andrew

Posted : 20/06/2020 6:59 pm
morphias
(@morphias)
Eminent Member

I'm an electrician.

You are very lucky not to have had a fire!

You have a few issues there. As @andrewld said, it 'looks' like the terminals were overtightended given how off center they are.

Alternately, given all the burning and melting, they may not have been tightened enough and that has lead to 'hot joints'. A hot joint is where an electrical connection has insufficient surfance area conact for the current to flow. This reduced surface area means the same amount of current is still trying to get through, but can't. This causes heat due to the 'resistance' or 'opposition' of flow.

Think of it like a hose with a kink in it. The water pressure is still there trying to force it's way through. What ultimately happens is the hose bursts or blows the connector off back at the tap.

There isn't any acid in solder rosin (flux) unless you specifically purchase acid flux solder. Electronics manufacturers definitely do not use this stuff.

The board and PSU are likely salvageable if there are still functioning. They will need to be removed and VERY cafefully (so as not to damage any components) cleaned up. A soft bristle toothbush will help and a can of compressed air and electrical components cleaner. Your local 'Radio Shack' style store (Jaycar or Altronics in Australia) or electrical wholesaler will have it. I will say this again, VERY CAREFULLY! You are not scrubbing rust off a piece of steel with a wire brush. 🙂

Something like this: https://crcindustries.com.au/products/crc-co-contact-cleaner-350g-2016.html

The cable compatability will simply be the length of the cables given the different route they take with the different models of PSU.

As @andrewld said, get new cables made from high temp silicone insulated wire of no less than the current gauge. Bigger is better, but definitely not smaller or you will get into the hot joint issue again.

It does look like you may need a new power panic cable, but it's hard to tell from the pics.

You need to support the crimp terminals when you tighten them. Don't let them twist into the plastic separators and leverage against them. They are not deisgned for that. They are there as electrical separators to prevent dead shorts.

After everything is reassembled, you could give the terminals a spray with an electronics preservative to stop the air getting to the copper in the cables. Not sure where you live, but salty air can cause the patina (the green 'growth) you can see. This also causes hot joints.

https://crcindustries.com.au/products/crc-2-26-electrical-multi-purpose-450g-2005.html

 

For the record, I have no affiliation with CRC Industries - they just make excellent products and I use them daily in the course of my job - a lot of which is maintaining, repairing, designing and building industrial control systems.

 

Ben.

This post was modified 2 months ago by morphias
Posted : 20/06/2020 11:18 pm
danielsillar
(@danielsillar)
New Member

Thanks for the help Andrew and Ben!

The advice you gave is very useful, and I've removed the damaged wires and the Eisny board from the printer and given the board a clean with a soft brush. The power panic cable is undamaged, but the damage to the plastic around the negative bed out connection worries me due to your comment about potential fires, as it has melted inwards slightly and as such i cant fit a metal connection head inside without it touching at least some of the surrounding plastic.

I've added some clearer pictures below

Thanks again for your help, and its a relief to hear I at least wont have to be buying a new PSU!

 

Regards,

Daniel

Posted : 21/06/2020 7:20 am
Andrew
(@andrewld)
Estimable Member

Do not connect to that board in its current state. any protection once offered by the plastic separators is gone and (depending on the material used) can conduct electricity when melted and solidified. If your skills are up to it you can replace the plastic and connectors, if not buy a new board. It's really not worth "taking a punt" on fixing it if your not sure what you are doing.  No offense or slur intended.

As for the corrosion, that's till a mystery as to why . Loose tails (connections) can arc and cause overheating and will accelerate any dissimilar metals reacting together. But the only times I have seen that type of corrosion in an electrical installation is in boats and cars where the salt water has got to it or where the wires are exposed to the elements

AndrewP.S.

Ben

As to no acid in flux...you've never seen a plumber having a go at electrics?.... 🤣 🤣 🤣 

AD

Posted : 21/06/2020 11:10 am
charles.h13
(@charles-h13)
Famed Member

Be very careful.  I had this same issue and almost has a fire after restarting the printer.  It worked for a few days and then I smalled burning plastic with and ABS print.  One of the cables gad loosened.  

Posted : 21/06/2020 11:10 am
danielsillar
(@danielsillar)
New Member

Yeah I suspected as much, and replacing the plastic and connectors is definitely beyond me - no offense taken.

Seems like getting the replacement cables for the silver PSU is going to be a bit tricky but a lot better than the $150+ aud a new unit costs.

Cheers for the help guys, going to mark this one solved.

Posted : 21/06/2020 11:50 am
Robert-mm200
(@robert-rmm200)
Noble Member

Factory has been known to put out a few power cables with bad crimps. Those will overheat and show all the symptoms

you observe. It is worth investing in a good crimper - and make your own cables. It is not hard. And sure cheaper than buying a new EINSY board.

Don't reuse your current cables unless you crimp new connectors on.

Posted : 22/06/2020 6:23 pm
Karl Herbert
(@karl-herbert)
Famed Member

@robert-rmm200

For this reason, i modified my printer (24V power, nozzle/bed thermistor, heatbed) with heat-resistant and flexible silicone cables (new molex connectors) before starting up:

https://www.conrad.com/p/lapp-0084010-heat-resistant-cable-olflex-heat-205-sc-1-x-1-mm-transparent-sold-per-metre-603221

This post was modified 2 months ago by Karl Herbert
Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen....
Posted : 22/06/2020 6:51 pm
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