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burned out positive lead to the heatbed, how to fix?  

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maxminh
(@maxminh)
New Member
burned out positive lead to the heatbed, how to fix?

It may have been too cool in my room, when I was printing. So the heatbed likely pulled too much current. I got the message

"Bed thermal runaway error" and smelled fried electronics or wired. I check the fuses and they are fine, but the positive lead to the heatbed is fried.

Below are two pictures of the positive lead:

fried lead

fried lead 2

Can this be fixed? If so, how?

Thanks for any help the community can give me.

 

Posted : 13/10/2019 11:43 pm
JoanTabb
(@joantabb)
Moderator
RE: burned out positive lead to the heatbed, how to fix?

The heatbed cable flexes a lot during printing. 

Prusa have used better than average cable  however there is better cable to  be had. 

other issues can also reduce the lifespan of the power cable.

I have replaced my heatbed power cables with 16AWG flexible silicone insulated cable, 
I made the cables a little longer to reduce the overall flexing.   

all of my printers have braided cable covers, and all have Nylon filament reenforcement in the X and Y cable bundles.

the wire I use is like this

the flex cable on your printer mains cable typically has seven strands in each conductor, 
the Prusa heatbed has about 21 strands and 

the silicone flexible cable above has 252 strands   making it much more flexible

regards Joan

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK...
Posted : 14/10/2019 12:00 am
richard.l liked
maxminh
(@maxminh)
New Member
Topic starter answered:
RE: burned out positive lead to the heatbed, how to fix?

Thanks Joan.

Posted : 14/10/2019 12:57 pm
rmm200
(@rmm200)
Noble Member
RE: burned out positive lead to the heatbed, how to fix?

After you fix it -

There should be no flexing at the connector in use. If it does flex - you did not secure the cable casing correctly.

Posted : 14/10/2019 3:41 pm
maxminh
(@maxminh)
New Member
Topic starter answered:
RE: burned out positive lead to the heatbed, how to fix?

Replacing the wire is not my main concern. I was wondering if damage to the lead on the

circuit board as shown in the second picture of my originally post and in a better picture below:

close up of burnt positive lead

can this be repaired?

Posted : 14/10/2019 4:05 pm
JoanTabb
(@joantabb)
Moderator
RE: burned out positive lead to the heatbed, how to fix?

That looks like the connector was loose or incorrectly fitted...  

check the solder joint to the PCB, is that ok?
If the screw plate can be cleaned up, and the spade terminal is OK, or new spade terminal, 
I would re assemble with a smear of petroleum jelly on the contact to prevent future oxidation and try it out again,
other options are,

remove and replace the connector strip,

solder the wires on to the PCB

Solder a different high current connector to the PCB  + cable and use that...  good quality XC30 connectors can handle the power  XC60 connectors are bigger and easier to work with... 

 

regards Joan

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK...
Posted : 14/10/2019 5:23 pm
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 --
(@)
Illustrious Member
RE: burned out positive lead to the heatbed, how to fix?

If there is any carbonized FRP (the board material), it needs to be repaired or you risk a fire.  

Posted : 14/10/2019 6:17 pm
maxminh
(@maxminh)
New Member
Topic starter answered:
RE: burned out positive lead to the heatbed, how to fix?

Thanks Joan and Tim. I will need to look into it when I have more time.

Posted : 15/10/2019 11:37 pm
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