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partial_accumen@lemmy.world ⁨6⁩ ⁨days⁩ ago

The photo isn’t great, but it looks like a 6-pin package. From your schematic I would assume its part of the battery charging circuit.

You say it “blew” is it shorted or open? If open, then my guess is the rest of the device should function, you just won’t be able to charge the battery. If its shorted, I could see that draining any current away from your piezo driver.

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bruce965@lemmy.ml ⁨6⁩ ⁨days⁩ ago
Sorry about the pictures, that’s the best I could do with my phone camera. I took some more, they are not much clearer, but there are more angles at least, link to pictures. It certainly is a 6-pin package.

It didn’t occur to me that it could be part of the battery charging circuit, that would be nice. I am a bit worried about plugging batteries again, as I am afraid I might damage it further. Assuming pins on the left to be 1, 2, 3 from the top and pins on the right to be 4, 5, 6 from the bottom: pin 1, 2, 5 and 6 seem to be shorted, pins 3 and 4 give me 90k resistance.

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

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- partial_accumen@lemmy.world ⁨6⁩ ⁨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.
  
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  - bruce965@lemmy.ml ⁨6⁩ ⁨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.
    
    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, as other similar designs omit it. I’ll try desoldering it and see if it works. Thank you very much for this suggestion, that blew my mind!
    
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- jeinzi@discuss.tchncs.de ⁨5⁩ ⁨days⁩ ago
  There’s no way U1 is charging the battery. How would it? If the connection labeled USB is the power source, it’s only connection to U1 is through a 100k resistor and a reverse biased diode. Also, charging AA batteries? Sure, you could plug in some NiMH cells, but then the device would need to have explicit instructions telling you that this is indeed a charger and to only ever insert rechargable AA battery cells.
  
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  - bruce965@lemmy.ml ⁨5⁩ ⁨days⁩ ago
    Fair point. There were no such instructions.
    
    I tried desoldering U1, disconnecting the piezo, and powering it with 3V from the batteries side. It blinks rhythmically, so I assume the MCU (or ASIC) is fine. But if I connect the piezo, power consumption drops to < 1mA and nothing else happens. So yeah, that component’s purpose is probably not to charge the batteries.
    
    I will try to read the markings again with a magnifying glass later today. Unless you or someone else have better suggestions.
    
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