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What happened:

Two of the blue wires touched while an 11.1v battery was hooked up and POP

What's in the photo:

  • Yellow is the heat shrink wrapper I cut open
  • the material with square impressions on it from the ICs is the heat sink
  • My fingers are holding apart the heat shrink so you can see the burn
  • The burn is from the damage of the two blue wires connecting.
  • the PCB is flipped upside down so you can see the spot where the burn came from

It looks like the lowest left IC is a little melty on top so I'm thinking something fried in there. How do I check if that's bad? I have a multimeter and I'm prepared to use it I'm just not sure what to do.

EXTRA

This is an Electric Speed Controller for a brushless motor. The motor was spinning when two uncovered bullet connectors (from the blue wire side) touched and made a spark. After that the motor wouldn't spin it would just spaz out, acting like only 2/3 wires were working (understandably so).

burned out esc

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  • \$\begingroup\$ Welp, that transistor's gone. At the very least you'd have to grind it off and replace it. \$\endgroup\$ – Ignacio Vazquez-Abrams Mar 1 '15 at 2:42
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    \$\begingroup\$ @IgnacioVazquez-Abrams - Grind it off? Why not just desolder it? \$\endgroup\$ – Connor Wolf Mar 1 '15 at 2:47
  • \$\begingroup\$ If you have the gear to desolder a D-PAK without delaminating the board then that's another option. \$\endgroup\$ – Ignacio Vazquez-Abrams Mar 1 '15 at 2:55
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    \$\begingroup\$ If you're not trying to save the part D-PAKs are easy, clip and desolder the legs, then the body. \$\endgroup\$ – Matt Young Mar 1 '15 at 3:08
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Thats too bad, thankfully the solution is easy(ish)

  1. Read the top of the other chips next to the blown one (I am optimistic that they are all the same)
  2. Google the part number (typically the first/top line), and order a replacement (good sellers are digikey and mouser)
  3. Clip the 2 legs of the blown component
  4. Desolder the legs, be careful not to lift the pad!
  5. Let the board cool for a bit
  6. Desolder the component, again be careful not to lift the pad..
  7. Let the board cool for a bit
  8. Clear off the old solder with some solder wick.
  9. Let the board cool for a bit
  10. Solder the replacement on.

When desoldering, I like to heat up the component and then with my other hand, grab the component with tweezers. Sometimes, it actually helps to add solder to the part, if it is being especially stubborn. Always watch and make sure that you are not about to lift a pad.

In case the worse happens, and you lift a pad, use your eyes, and if needed a multimeter to find out where the trace on the board goes. Solder a wire from where the lifted pad was, to where the trace goes. Just pay attention to how much energy is flowing through the wire, and properly size the wire.

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  • \$\begingroup\$ There will be 3 N-type and 3 P-type MOSFETs on there eh? Quite possible that all four devices involved in that pair of wires are blown. Some investigation with a 'scope is needed first. \$\endgroup\$ – tomnexus Mar 1 '15 at 6:00
  • \$\begingroup\$ For the average person who does not have access to a scope, that may not be possible. Replace the obviously bad one first, it is a bit of a hail marry, but there is a good chance of it working. \$\endgroup\$ – Reid Mar 1 '15 at 6:20
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    \$\begingroup\$ True, if it was a thermal problem the others might have survived. I would still buy two of each transistor, if I'm paying for shipping. \$\endgroup\$ – tomnexus Mar 1 '15 at 6:46
  • \$\begingroup\$ Good point! Hey, might as well by all the fets needed if they are cheap too. \$\endgroup\$ – Reid Mar 1 '15 at 13:51

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