Hi! I recently purchased a nice gadget from AliExpress, this should be the circuit to drive an ultrasonic piezo. Silly me, I put the batteries backwards and the U1 component on the bottom left blew up.

I know a bit about circuits so I reverse engineered it (there might be mistakes), but I am not skilled enough to identify the component in order to look for a replacement. Can someone help me identify it? I can read ___22 on it.

Here’s another version of the schematic, which might be easier to understand.

Schematic

Thank you for your help!

EDIT: I couldn’t identify the component, but I did a Google Image Search as suggested by @partial_accumen@lemmy.world and it found similar PCB designs. It very much looks like this component is part of the charging circuit, which I do not particularly care about. I will try desoldering it and see if the rest of the device still works. I will post the outcome here.

EDIT 2: with a lot of help from @jeinzi@discuss.tchncs.de I managed to fully reverse engineer it and fix most of the mistakes in the schematic. That component was just an FP6291 after all, part of a circuit to step up the 3V from two AA batteries to 5V required by the MCU. I replaced that whole section with a step up module I had previously purchased from AliExpress, and now everything works again.

Here’s the final (mostly accurate, hopefully) revision of the schematic.

Schematic Revision
(link)

Lessons learned:

  • Always double-check battery polarity
  • In the age of AI, Google Image Search can now help identity circuits
  • Sometimes a circuit that looks complex can actually be much simpler in the end
  • AskElectronics@discuss.tchncs.de amazing community on Lemmy

That was fun! Thank you very much to everyone who contributed to this thread!

  • partial_accumen@lemmy.worldEnglish
    4·
    24 days ago

    It didn’t occur to me that it could be part of the battery charging circuit, that would be nice as honestly I don’t care about using it as a battery charger (it takes two AA).

    I’m a bit confused. Two AA batteries usually means 3v DC which is common to power a device. However, in your schematic on the left hand side, you have a symbol that represents a battery, its labeled 5v, and USB. I assumed this was the power source for the device. If not, why does your device have two power sources and one is not rechargeable.

    I didn’t try image search, do you mean on Google Image Search?

    yes

    • bruce965@lemmy.mlOPEnglish
      3·
      24 days ago

      If not, why does your device have two power sources and one is not rechargeable.

      That’s a good question, and that’s also something else I didn’t think about. I just checked the instructions and it’s not clear. Perhaps it’s an alternative way to power it. I’ll be honest, this is a cheap device. I don’t want to fix it because it’s expensive, I want to fix it because I literally didn’t turn it on even once before blowing.

      I drew it as a battery, but that’s actually USB power (5V). That was probably a poor choice from me.

      try image search

      Oh. My. God! It worked! How on earth could it know that this specific PCB is what it is? That’s black magic! It didn’t find this specific one, but it correctly classified it and it also found similar designs. Seems like that blown component actually is part of the charging circuit, since other similar designs seem to omit it. I’ll try desoldering it and see if the rest still works. Thank you very much for this suggestion, that blew my mind!