I have the mx3 sparrow with 4 in 1 esc 28A and PBF3 Evo F3. Two of the CW motors are not working and I think I know why but I’m not sure. In the esc, there are little pins in the mosfet and because they are to close to the motor’s soldering pads the pins solder together. I wanted to know will it fix the problem if I will remove all the solder.
I’m not sure.
But I don’t think it helps.
Its worth a try to clean it up and see if it helps
Yeah, it is hard to know for sure without testing properly, an easy trick ot to sleep for anything burnt on the esc. If not, Iwould try to get some solder wick to clean it up as maybe it will still work, but if not then you will need to buy a new 4in1 ESC 
This is the problem because it’s geprc I will have to buy new mini tower because they don’t sell just the esc board
And the pins in the esc connect to the fc
there are only 3 beeps on startup insted of 4 what can i do
From your photo it looks like HGLRC is the manufacturer of the FC, so if you can identify which FC it is, you should be able to figure it out and buy one from someone who sells HGLRC stuff. As it looks like GEPRC are just using a rebranded HGLRC flight controller?
I bought a new FC (HGLRC XJB OMF4 ) but I’m not sure if it’s the right one because the drone only powers up while connected via usb.(when the usb and the battery
are connected to the drone I can power up the motors and when I try to connect the battery alone there are 3 beeps from the motors and then nothing happens)
Yes you are right they are using HGLRC
