[Solved] RUMBA burned

Hello,
Today I sadly had the idea to update the cable that goes from the DC power to the Rumba board, I switched the polarities by error and when I turned on the printer I saw a smoke puff. Quickly I turned it off, found the reversed cables and placed them correctly.
Now the LCD does not lights up, the board does not show any other light blinking or on. I have checked the Rumba board and I can see a small black cube marked with an "M7" burned, I think it is a M7 diode but don't know for sure:


Did you have a similar issue in the pass and there is any quick solution to fix the board?
Could anyone point me out what this small thing is in order to try to buy a new one and solder it?
I hope I can fix it instead of having to buy a new one... I'm so sad about it because before everything worked flawlessly.
Thanks in advance =(

edit: in my last post I explain how to solve it =)

Edited 1 time(s). Last edit at 01/08/2014 11:45AM by dolphinboy.

Can you desolder that diode? Looking at the schematic it looks to be D6.

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- akhlut

Just remember - Iterate, Iterate, Iterate!

[myhomelessmind.blogspot.com]

Yes, I think it's possible. As you say, it should be D6, it has sense...
What I don't know is how to get it's specifications, I don't know if I go to a electronic store and say "M7 diode as this burned one" they will be able to give me the exact one...
Is there a BOM with the components of the Rumba board? I can't find it in the wiki.

Thanks akhlut!

Today I'm happy again, I solved it!

As askhlut pointed out (thank you!), it was the D6 diode. I went to an electronic store and they sold me a generic diode that works for 24-35V. I desoldered the burned one, soldered the new diode and voila, it seems everything works perfectly so, if anyone connect by error the DC cables with the incorrect polarities it will surely burn the D6 diode, in fact, I guess it is designed to protect the rest of the board, of course, burning itself but cutting the connection between the power supply and the Rumba board; and so, the solution is to remove the burned one and solder a new one (it only cost 5 cent of euro).

=)

Good! Some folks would have tossed the board for a new one. Better to repair than replace.

While the RUMBA is 'open source' it's not very friendly. It's designed in Altium (I can't imagine how expensive a seat is), so you can't open the files to generate a BOM.

Honestly, you really don't even need that diode - it's just there to protect the electronics in case of a polarity reversal. But a few cents of insurance is worth it.

When that diode fails it needs to fail-closed, otherwise it would allow the reversed polarity into the downstream circuit.

Just be careful next time you hook up your wires.

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- akhlut

Just remember - Iterate, Iterate, Iterate!

[myhomelessmind.blogspot.com]

Yes, it was not only cheaper but quicker , I can't imagine myself waiting 2-3 week till the new board arrives home...

Once you pointed the D6 diode I realized about its importance in the board: to prevent a reversed polarity to go inside the other components, and yes, I thought it probably was not necessary to hae the diode =)
The funny thing was that it wasn't my fault but two connectors that I bought separately and from different brands, they were 3 wires cable and used for AC. One connector had Neutral and Line correctly and the other connector at the contrary; in AC it has no effect but as I used it in DC the result was the unexpected polarity inversion... At the end I have learn to pay attention to polarities and not assume that what I red in cable labels from unknown sources are the correct information, hehehe.

I hope this helps somebody for potential similar situations
And thanks again akhlut

I have the same problem but with a difference and that is that the main cpu get very hot and the it does not drive the motors.
I have changed the same diode already but the cpu still get very hot.

please advise.

Ummm, I really think your problem is not related with mine because once I inverted the power polarity by error the diode literally burned and totally stop working... it is not that it get hot, it burned and had to replace the element.