Hi all,

I know this is going to be a long shot, but I hope someone can give me some pointers.

So long story short, last week I accidentally plugged the battery incorrectly (spare battery with 2 pin JST connector).
I plugged it off right away because I saw I took the spare nimh batter that doesnt have the 3pin connector.
And then I plugged it back with my main battery and viola, nothing turns on.
Tried to take off the case to have a look at the board, but I can't see anything odd, can't see or smell any burnt chip as well.

Does anyone have any idea for me to look? I have multimeter but I have limited knowledge of electrical components.
Below is the picture i took, I dont want to overload the server therefore i uploaded to image hosting instead.
https://imgur.com/Ph87BK8
https://imgur.com/UHNsgqD
https://imgur.com/pciivrQ
https://imgur.com/8BRk4zE
https://imgur.com/TvUHdNa
https://imgur.com/94qNxvF
https://imgur.com/5ZUG6vC
https://imgur.com/6COrcDC
https://imgur.com/0h4euvg
https://imgur.com/OQSFuSe

Any help will be appreciated, thank you in advance!

With no knowledge and no real burning marks I wonder why the try? It sounds to me that when even you did found something you still are not able to fix it.

But this pic is the battery connection?
https://imgur.com/5ZUG6vC
Looking at it it seems there is a SOT23 diode, FET or transistor on it

This pic: https://imgur.com/6COrcDC
Going down from display, 4-pole connector, switch... Right under the switch I do see someting like a voltage regulator., that one it probably defect.

Im trying to find out if the controller is fixable since I still want to use it for couple more months before upgrading.

That is correct, thats the 2 pins battery connection which I plugged in incorrectly.

I will double check this chip again, if I remember correctly I could still see 6V going through the pins but I might be wrong.

Added more close up picture.
https://imgur.com/eVG7CPe

Seems like this....
https://nl.mouser.com/datasheet/2/268/22053C-476082.pdf

9B2 is the package code of a 3.3v version and pin 1 and 5 seems correct with the capacitors.And pin2 looks like indeed a ground.

SMD packages are hard to find out what is inside. On your pic I do see 6 pins while my founde regulator with a matching SMD code (9B2) should have 5 pin. Hard to see because exactly that pin is soldered a bit weird and pin 3 and 4 are looking different...
If pin1 gets the battery voltage and pin3 is also positive the output pin5 should be 3.3v.

I just tried to check the pins with my multimeter.
Seems like Pin 5 is outputting 3.3V and pin 4 is outputting 6V when the 6V battery pack is connected.
I can't find any other broken chips, therefore I will probably ditch the controller and just get a new one instead.
Its probably not worth the time to try to fix this.

I really appreciate your help!

So it seems there is 3.3v, so it must be something different behind the voltage regulator or there is a 2nd voltage regulator somewhere.