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!

  • bruce965@lemmy.mlOPEnglish
    1·
    5 months ago

    You must have spent a lot of time into this, thank you so very much 🙏

    With a bit of persuasion I managed to disassemble it without breaking it. I desoldered U1 and I can confirm that pin 2 is GND. Also, here are better pictures taken with a magnifying glass. Note that pin 1 and 3 were shorted to pin 2, but it didn’t make sense to me, so I assumed they bridged due to the thermal shock when the component burned, so I scraped around them.

    And here’s a link to AliExpress.

    I guess there is no easy way to bypass it then, it would probably cheaper to buy a new device than to buy a replacement IC. Also, I guess now I will have to upload a clean version of the corrected schematic, I owe this to you and the other great people that replied.

    EDIT: I could probably bypass it entirely, I just need to inject 5V. Here’s the updated schematic.

    Schematic