Uno R3 Clone - Fried Voltage Reg

I wasn't paying attention and grabbed the wrong power supply, 24v, from a box and plugged it into the DC barrel jack. It instantly fried the voltage regulator (AMS1117 5v) on my Uno R3 clone...No surprise there.

I removed the bad AMS1117 using a hot air gun and put on a new one. I then checked everything with a Multi-meter to make sure it was hooked up correctly.

Using the continuity setting, I got a positive continuity result between 5v and Gnd and between 5v and 3.3v.

Using the resistance measurement setting I got a result of about 34 Ohms between 5v and Gnd and about 23 Ohms between 5v and 3.3v.

None of those results are good.

I then took those same measurements on a completely working board: I got no continuity between 5v and Gnd an no continuity between 5v and 3.3v. For resistance I got about 3.1K Ohms between 5v and Gnd and about 2M Ohms between 5v and 3.3v.

I then removed the new AMS1117 that I put on but I still got the same bad results. I also removed the ATMega328P chip and still got the same bad results.

Obviously, I have some other component that is damaged but I'd rather not desolder every component randomly, one by one. I've looked over the board with a magnifying glass but I can't see any other noticeable signs of damage.

Does anyone have any guesses as to what other components could have been damaged or could the PCB traces have been damaged?

Really hard to say, there are some “sensitive” components which could be damaged. But which one to name first?

  • ATmega16U2
  • another regulator for 3.3V
  • OAMP
  • transistor
  • fuse
  • ferrite bead
    EDIT: What about filtering capacitors? Especially on input.

I removed the 3.3v regulator and now continuity between 5v and Gnd and between 5v and 3.3v is gone and the resistance measurement between 5v and Gnd has gone up to about 1.5K Ohms but it’s still not the same as the 3.1k I get from a working board.

My guess is that something else is probably fried, too. At this point, it was a fun exercise in a small amount of troubleshooting but it’s no longer worth it to keep removing parts one by one, ordering a pack of them from China and replacing them just to fix a board that I can completely replace for $11.

Thanks for your suggestions.