Finding component

Thread Starter

Davor96

Joined Apr 20, 2020
6
Hi,

I need help identifying which component was in a circuit on PCB.
I improved the battery capacity of my portable speaker for about 20 times.
Before there was 600mAh Li-ion battery and now I made slots for 5 18650 batteries.
Once I accidentally placed battery reverse and smoke came off.
I removed PCB from the speaker and found a burned component. It is sot23 standard but I don't know was it transistor, mosfet, zener ect.
because it is burned. No other components were damaged.
If pins are:
----1----
2------3
pin 3 is directly connected to Vcc.
Pin 1 is directly connected to the condensator.

When I connected battery properly:
Before I removed component voltage on pin 1 it was 2.7V but it sometimes drop to 1.8V and voltage on pin 2 was 3.8V. (Pin 3 Vcc(4.04V))
After I removed component voltage on pin 1 was 0.3V and on pin 2 it was 3.6V.(Pin 3 Vcc(4.04V))

Without battery and removed component:
pin 1 --- bat ground = resistance goes up(condensator is probably charging).
pin 2 --- bat ground= no readings
pin 3 --- bat ground= no readings

pin 1 --- bat Vcc(or pin3) = no readings
pin 2 --- bat Vcc(or pin3) = 10kOhm
pin 3 --- bat Vcc = direct connection (0 Ohm)

When I set the positive probe of my multimeter to pin 1 and Com to 2. I got reading for a brief moment(but only in continuity test 1500-1900, in Ohm scale, there is not even a reaction).

When I apply 3.3V to the + terminal of the condensator speaker works perfectly. (Ground is connected to the battery ground)

1st I thought that it is 3.3v regulator but I wasn't sure because pin 2 is not ground.
2nd I thought that it is PNP transistor or Mosfet but I don't know for sure and don't want to break circuit more.
 

Thread Starter

Davor96

Joined Apr 20, 2020
6
Yes,
that one it was really burned, radio was at first constantly turning on/off(fm starts working and after less than second it turns off), after some testing, it fell off from PCB.
 

Thread Starter

Davor96

Joined Apr 20, 2020
6
For now, I just bridged Vbat directly to capacitor + till I find out which component is it. And now I don't have a protective circuit and if I accidentally switch battery bye bye radio.
 
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