Fried heatbed connector...

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Fried heatbed connector...

Postby DonaldJ » 2013-Nov-Thu-01-Nov

This problem came out of the blue.

Set up a project, and I noticed the printbed wouldn't heat up. Checked the connection points on the heatbed and it wasn't getting any juice. Pulled the connector from the Printrboard and noticed scorch marks on the plug. When removing wires from connector the plug broke and I could see it was *really* fried. The pins on the Printrboard are okay; output is 12+ v.

Any ideas on the cause? Printer was working fine earlier today until it quit after 5 hours due to laptop entering hibernation mode. Other than that, absolutely no problems after a few days of 10+ hour printing sessions

At least I have some PLA I can try out ;-)

scortch1.jpg

scortch2.jpg

scortch3.jpg
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Fried heatbed connector...

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Re: Fried heatbed connector...

Postby gyronictonic » 2013-Nov-Thu-09-Nov

Welcome to the burnt connector club. The large 8" x 8" hot plate pulls in a good amount of current and the connectors just can't handle it. This happened to me twice already but I figured out a quick fix. If you are using a PSU, look and see if you have this 4 pin connector in the link below. If so, you should be able to use that as a replacement. It's a bit beefier and it will fit if you push it in hard enough.
http://0.tqn.com/d/pcsupport/1/0/3/7/-/ ... -molex.jpg
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Re: Fried heatbed connector...

Postby RetireeJay » 2013-Nov-Thu-09-Nov

The heatbed circuit uses two wires in parallel to carry +12V to the heatbed, and two wires in parallel to carry (switched) return current to ground through the MOSFET.

However, the connection of these wires at the heatbed end is subject to flexing fatigue. Wires that have solder in them are extremely easy to break. So what may have happened is that one of your two red wires or one of your two black wires broke off at the point where they are soldered to the heat bed.

One of the rules of electricity is that "current going = current returning."

Let's say that your heatbed draws 10 amps. Let's say one of the black wires broke. Now you have two red wires, each red wire carrying 5 amps but one black wire carrying 10 amps. That double current on the black wire will cause the black wire itself to get uncomfortably warm, and it will definitely exceed the rated current for passing through that connector at the board. Thus the connector will overheat.

So check the wires at the point of connection to the heatbed and fix if necessary. Then be sure you use a zip tie to immobilize the wires as they leave the solder joint. Let them flex farther out, but keep the solder joint stable.
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Re: Fried heatbed connector...

Postby DonaldJ » 2013-Dec-Fri-18-Dec

Finally made the fix as suggested, and it works swell. A little Dremel work on the ridge of that connector made it fit with no problems.

Thanks to you both.

I did enjoy going through that kilo of PLA I had laying around, though.
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Re: Fried heatbed connector...

Postby lwalkera » 2015-Jan-Tue-12-Jan

I would highly recommend replacing the stock wires with silicone insulated wire soldered directly to the pin headers (<rev D) or connected directly to the screw terminals (rev F).

http://www.amazon.com/ACER-Racing-Gauge ... 007ZIWFBC/

Wires soldered to the headbed connector:
Image

You can see the connectors here:
Image
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Re: Fried heatbed connector...

Postby DonaldJ » 2015-Jan-Tue-23-Jan

lwalkera wrote:I would highly recommend replacing the stock wires with silicone insulated wire soldered directly to the pin headers (<rev D) or connected directly to the screw terminals (rev F).


I just saw your response to this old post because the connector fried again, as discussed here: viewtopic.php?f=15&t=8970

I have a bunch of connectors, and I was able to repair the 'bot without removing the board. If I have the problem again I will definitely pull the board and do a more robust fix.

Any thoughts on the voltage drop?
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