Hello,
I have racestar f4s and when it’s plugged via USB to my laptop nothing happens, like if it’s not plugged, and an IC  on the FC becomes so hot (I can’t keep my finger on it ), and the red led is slightly On , and the same happens when I plug the battery just the red led becomes brighter and the buzzer makes 3 beeps .
my USB cable is data cable and works fine, just yesterday everything was good, I was testing my motors from betaflight and also my receiver till this morning I want to plug it to complete the configuration and  (this is my 1st build, it didn't fly till now).

If it's getting that hot then unfortunately it sounds like something has gone bad on the FC.

Do a continuity check between the LiPo BAT+ and BAT- pads, and also do a continuity check between the a 5V pad and a GND pad to see if you have a short. Also inspect the board with a magnifying glass for any stray solder balls and check that you don't have any stray strands of wire from a soldered connection bridging across to something else.

You can also check the continuity of the VCC and ground on the MCU. If you get continuity there, that means the MCU is toasted. But hot MCU is usually a clear sign that it is done for as Snow said.

(07-Oct-2019, 08:59 PM)SnowLeopardFPV Wrote: If it's getting that hot then unfortunately it sounds like something has gone bad on the FC.

Do a continuity check between the LiPo BAT+ and BAT- pads, and also do a continuity check between the a 5V pad and a GND pad to see if you have a short. Also inspect the board with a magnifying glass for any stray solder balls and check that you don't have any stray strands of wire from a soldered connection bridging across to something else.

thanks for your reply, I checked the continuity nothing shorted I also unplugged everything from the FC and the same problem.

(07-Oct-2019, 10:57 PM)voodoo614 Wrote: You can also check the continuity of the VCC and ground on the MCU. If you get continuity there, that means the MCU is toasted. But hot MCU is usually a clear sign that it is done for as Snow said.

nothing is on the mcu ,just a tiny ic which gets so hot
https://ibb.co/TvB95jb


<a href="https://ibb.co/TvB95jb"><img src="https://i.ibb.co/7YJsFMR/IMG-20191006-172619-2.png" alt="IMG-20191006-172619-2" border="0"></a>

I can't see your photo. But it might be good news, depending on what IC you are referring too. I just assumed you meant MCU when you said IC.

(08-Oct-2019, 01:49 AM)voodoo614 Wrote: I can't see your photo. But it might be good news, depending on what IC you are referring too. I just assumed you meant MCU when you said IC.

https://ibb.co/TvB95jb

(08-Oct-2019, 10:15 AM)LRH18 Wrote: https://ibb.co/TvB95jb

That's a voltage regulator which will either be for the 3.3V rail that powers the MCU, or for the 5V rail that powers all the 5V stuff including external devices. If it's getting hot then it has fried itself.

What letter / number identifiers are written on the top of it?

Just looking at your picture I see a couple of things to question



Red wire to ground and black wire to 5V ?
Can't see the other end of the wires but that is not good practice. Red is usually V and black is Gnd.

Scott

(08-Oct-2019, 01:17 PM)Scott_M Wrote: Just looking at your picture I see a couple of things to question



Red wire to ground and black wire to 5V ?
Can't see the other end of the wires but that is not good practice. Red is usually V and black is Gnd.

Scott

they are also swapped on the receiver side and the receiver was working fine ,I took everything off and the pb still exist

(08-Oct-2019, 10:28 AM)SnowLeopardFPV Wrote: That's a voltage regulator which will either be for the 3.3V rail that powers the MCU, or for the 5V rail that powers all the 5V stuff including external devices. If it's getting hot then it has fried itself.

What letter / number identifiers are written on the top of it?

Thanks for ur reply
what's written on the IC is IL312