First time builder here and I think I have fried something on my flight controller. 
This Omnibus F4 Pro V2 was purchased from BG and is surely a clone.. sorry I wasn't aware about cloned boards at the time.  Anyway I am ordering an original Flip V3 board replacement, but would like to attempt a repair on this clone for practice.

How it happened: I was connected to the BetaFlight configurator via USB, when I figured I would connect my 4S LIPO to test if the motors would spin up, big mistake?! It immediately disconnected and I have not been able to re-establish a connection since - I just get a solid green PWR LED, no flashing blue LED as before.
 
I have tried all combinations of the DFU button, USB only, LIPO then USB, desoldered the receiver then all of the ESC's, testing at each stage, etc.. I don't get any response on the USB, not even an unknown device.

I now have a bare flight controller and  if I plug in the 4S LIPO it starts to smell like something is ready to burn, so I have quickly disconnected and haven't tested further..

When plugged into USB, the IC at U6 gets too hot to touch, so I suspect that to be shorted or something close by. As per the photo, the marking on the chip is A2PL and "U6" on the Flip silk screen. There are a few of these IC's on the board.
 
I need help identifying and sourcing a replacement part but I have tried searching google, digikey, mouser, ebay, aliexpress, etc.. and can't seem to get any hits!!
 
If I measure the current with my keweisi it is saying the board is drawing about 0.2A. I can't find any shorted diodes on the board or obviously burnt components. just the A2PL that is roasting hot.


Please let me know what else I should test, how to find the A2PL datasheet. Thanks.

The device that's getting really hot is a 3.3V LDO regulator - it most likely provides power to the CPU.

So either you have blown up the regulator, or the CPU.

How exactly did you have things connected when you plugged the battery in?

Motors and ESCs were connected to the PDB - it's just a simple plate with no BEC.
Battery was connected to the PDB and through to the FC via the leads as shown in the last picture - so not wired to use the current sensor.
ESC signal wires were connected to the FC.
The receiver (FrSky XM+) was installed and powered off the FC's 5V - it is still working and working off the board when in it's current broken state.

As above I was connected and powered via USB and working in BetaFlight. I then connected the 4S LIPO.. and dead. I think I may have fumbled the LIPO connection so it was sort of a on/off/on/off flickering connection as well.

I had earlier connected LIPO when not attached to the USB and the ESCs played the expected boot up tune. So I don't think it was the LIPO on it's own, but the combination of USB+LIPO.

I've since learned about data only USB cables and will make one for future safety.

I'll try probing the A2PL and see if I can find 3.3V on any of the legs and compare to the other A2PL's on the board.

Results are in:

Had ~5V on the in pins (3 leg side, left and right with ground in the middle) and only getting ~1.45V out on the overheating one (left on 2 leg side, right is 0V with no continuity to ground.

Another chip was giving a perfect 3.3V out, but one on the back of the board was only 2.9V.

I'll take it out of circuit and test another day.

Just need to find a datasheet and where to buy some..?

Datasheet: http://ww1.microchip.com/downloads/en/De...ic5205.pdf

Sourcing: eBay is your friend.

If you were not using the current sensor, what was the point of wiring the battery to the flight controller? All you needed were two very thin wires to power the flight controller and then have the battery wires connected to the PDB.
Still, connecting the battery while powered via USB wouldn't blow anything up. There's a bunch of Schottky diodes that isolate the various 5V sources from each other. I guess you were just unlucky.

Thanks for the data sheet, I've ordered 10 for $2.50 and will update on how it goes in about a month when they arrive. 

I do plan to use the current sensor and that is the reason I used the big wires. But because I didn't have any real documentation for the FC and it's my first build, I made a slight mistake and wired from battery to PDB to FC... as I'd seen in so many youtube build videos "without current sensors".   It's an easy fix and I will address that on the re-build.

Fingers crossed that the regulator is hot because it has failed and not because the CPU is overloading it.

Keep us posted!

(30-May-2017, 05:04 PM)unseen Wrote: Fingers crossed that the regulator is hot because it has failed and not because the CPU is overloading it.

Keep us posted!

Hi
You are not just unlucky.
I fried 2 in that way.

The first only connected to a Spektrum sat receiver, usb and 4S lipo. 
All setup and ready for ESC connection. The 4S killed it right away. 
2 x 3.3v reg. wrong voltage and hot cpu.

The second was only connected to usb and 4s lipo. Alle was fine for 5 minutes and I could read the right voltage on the screen and when I was setting up for the receiver it lost usb connection and died.
One hot mic5205 and 4,4V out. the one on the other side. CPU normal.

Both green light

Regards Rikard

If the regulator gets hot, then most likely something is shorted and the regulator itself is good.
Get a multimeter and check continuity between 3V3 and GND on the MCU. If it beeps, then most likely the MCU is bonkers.
After that if I were you, I would remove the MCU with hot air, check continuity again, and if it's gone - you have to salvage a new MCU. I have lots of them as I collect FCs as a BF dev, maybe you have some dead FCs with good F405 MCU somewhere in your toolbox :-)

Just had the same experience. Everything worked fine yesterday when I tested the motors, but today when connecting the USB and then the battery, it started to smell burned electronics. I unplugged everything and when I connected the battery or the USB cable, the green led was steady and the beeper was giving a constant "beeeeeeeeep" untill I unplugged it. It doesn't come up as a device in Betaflight GUI anymore either. Brand new Omnibus F4 V2 from Banggood

(27-Jun-2017, 09:09 AM)oyvinla Wrote: Just had the same experience. Everything worked fine yesterday when I tested the motors, but today when connecting the USB and then the battery, it started to smell burned electronics. I unplugged everything and when I connected the battery or the USB cable, the green led was steady and the beeper was giving a constant "beeeeeeeeep" untill I unplugged it. It doesn't come up as a device in Betaflight GUI anymore either. Brand new Omnibus F4 V2 from Banggood

Last week I got a hot air desolder and removed the MCUs and everything was right again. No heat, right voltages, just not running very well without the processor☺

(01-Jul-2017, 02:56 PM)atata Wrote: Last week I got a hot air desolder and removed the MCUs and everything was right again. No heat, right voltages, just not running very well without the processor☺

Haha, probably not

Banggood is sending me a replacement so we'll see how the new one works out. I have a feeling that there is something sketchy with this board

I have the same experience with the board, ordered from AliExpress. I finished setting up the board and it was connected to the computer. I connected a 4s lipo to test the motor direction. within 30 seconds, burning smell came out and the connection to betaflight was lost suddenly. later i found the two 3.3 volt regulator was too hot to touch. although the indicators glow, but no connection to computer. there is some definite hardware problem with these clone boards. I did not know it was clone until i got it.

Got the replacement board and it worked fine when connected to battery and usb at the same time. I haven't had the time to test it properly, but at least it worked for an hour or so while connected to a battery and usb on my bench