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I have an electrical board with 2 input voltages; one of them is 5V and another is 12V. I set 12V adapter to 5V absolutely in a wrong way. So I've found myself in a big problem.

Hope you guys help me to fix it so:

How can I find out which element has burned? I don't wanna to demount it, I put my board image for you if you wanna guess which part is commonly failed by over voltages.

enter image description here

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    \$\begingroup\$ Post a schematic? \$\endgroup\$
    – user57037
    Commented May 22, 2016 at 19:22
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    \$\begingroup\$ If any of them are getting hot when powered by the intended voltages, those would be suspect. Fortunately, the ones most likely to be damaged by overvoltage - the ICs - are socketed, with the exception of the heatsinked power driver which probably has two supply voltages and may not tolerate overvoltage on the lower. There do not appear to be many or possibly even any other active devices. As it stands, without more details of the circuit or observed failure mode there is not an answerable question here within the intention of this site. \$\endgroup\$
    – Chris Stratton
    Commented May 22, 2016 at 19:23
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    \$\begingroup\$ Question duplicated at Yahoo Answers so we might be wasting our time here :-( Also duplicated at Stack Overflow and it has already received suggestions at Super User \$\endgroup\$
    – SamGibson ♦
    Commented May 22, 2016 at 21:58

2 Answers 2

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I set 12V adapter to 5V absolutely in a wrong way.

So it's been subject to undervoltage? Outsourced guessing isn't a very productive troubleshooting strategy, but I'll bite.

I assume you meant that you applied 12v to the 5v input. If that's the case, the AVR micro is probably dead. The FT232 (or whatever constitutes the SMT serial-usb bridge on the bottom-side) is probably dead. The L298 might have survived, but it would be a miracle. The unknown PDIP-8 and TO92 packages are a mystery.

Start by creating a problem description. Are there any observed symptoms? What does it do or not do which constitutes incorrect behavior? What tests have been attempted? What was the nature of the voltage mismatch? Was it overvoltage? Improper sequencing? Reverse polarity? Was it applied for seconds or hours?

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I think that the cap next to the oscillator near the button at the top & C13, C14, and C20 may be damaged as well as some of the ICs.

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  • \$\begingroup\$ "cap next to the oscillator near the button at the top & C13, C14, and C20 may be damaged" - Why do you believe those capacitors have been damaged? Is it because of the marks they each have on the top? \$\endgroup\$
    – SamGibson ♦
    Commented May 22, 2016 at 20:12
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    \$\begingroup\$ If so then, FYI, such marking is normal on some disc ceramic capacitors - see 6th capacitor from the left in this photo from Wikipedia. This capacitor datasheet shows that the colour at the top can indicate the temperature characteristic of the capacitor in some cases. These coloured areas do not indicate burning or other damage. \$\endgroup\$
    – SamGibson ♦
    Commented May 22, 2016 at 21:01
  • \$\begingroup\$ Is this a sacastic answer? \$\endgroup\$
    – Sean Houlihane
    Commented May 22, 2016 at 21:55
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    \$\begingroup\$ This is simply wrong (ceramic disc caps tends to be rated for voltages far above those involved), and furthermore, guesses should generally be posted as comments rather than answers. Had you named electrolytic or tantalum capacitors, there might be a chance of damage but such a suggestion would be woefully incomplete without pointing out that the voltage rating is printed right on them, and polarity would only be an issue if the two supplies differed or the mis-connected supply had also been hooked up backwards. \$\endgroup\$
    – Chris Stratton
    Commented May 22, 2016 at 22:34

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