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3D printer heat bed burned connector

amnesia

Dec 26, 2021
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Hi all,
I have a problem with my Prusa MK3S 3D printer.

The bolt attaching one of the power lines to the heating bed copper pad became loose, and actually came off while the printer was operating. The arc created burned part of the pad off.
IMG_95491.jpg
Prusa 3D printer connector.jpg
Also, D1 (smd diode?) Looks like it may be blown, but I need to take it apart for a better picture.

The printer still seems to work properly, but I'm wondering if the current carrying capacity will be significantly decrease enough to cause premature failure under heavy demand. My options are to leave well enough alone and use it as is, or attempt to add a some copper trace and jumper wire to beef up the connection.

The plate is an expensive part, so I prefer to repair rather than replace it if possible, but I don't want to create a fire hazard either.

To give you an idea of the current flow through the connection, the replacement part is rated for 6.25 amps at 24 volts dc.

Any help or suggestions would be greatly appreciated.

Thanks, amnesia
 
Last edited:

Bluejets

Oct 5, 2014
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Doesn't look all that bad....I'm guessing there is another contact pad underneath that you didn't show .
 

amnesia

Dec 26, 2021
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Doesn't look all that bad....I'm guessing there is another contact pad underneath that you didn't show .

There was no other contact pad underneath the plate. I got a higher resolution version of the photo from my son (it's his printer). The supply voltage and ground are attached on top as seen in the picture.
Prusa 3D printer connector.jpg
 
Last edited:

Martaine2005

May 12, 2015
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That looks like arcing due to a loose connection but doesn’t look that bad.
Once tightened down it will be ok.
D1 doesn’t look like it was populated in the photo. Either way, it would have been for reverse polarity protection by the looks of it.

Martin
 

amnesia

Dec 26, 2021
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Actually, it turns out D1 is an LED which simply indicates that the heat bed is on, and its working so no problem there
 

Martaine2005

May 12, 2015
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R1 must be it’s current limiting resistor then.
Once that terminal is tightened down, it shouldn’t have any problems.

Martin
 

Bluejets

Oct 5, 2014
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If there is no contact or trace under the board ( which we cannot see) then the board will have to be multi layer.
That then would rely on a via which does not show either.
 

amnesia

Dec 26, 2021
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If there is no contact or trace under the board ( which we cannot see) then the board will have to be multi layer.
That then would rely on a via which does not show either.

Why would it be a multi-layered board? It is just a heating element. The smd resister/led between the connectors is just an indicator that the heater is on and probably just attaches to connectors. The only other component is a thermistor attached to the underside if the plate.
 

Bluejets

Oct 5, 2014
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Why would it be a multi-layered board? It is just a heating element. The smd resister/led between the connectors is just an indicator that the heater is on and probably just attaches to connectors. The only other component is a thermistor attached to the underside if the plate.

For one thing, there is a contact plate on top but no visible trace to the heater element or whatever.
Op says there are no contacts and I assume , no traces underneath so therefore it stands to reason they must be internal.
 
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