Hello,

I started having an issue, probably from a bad solder on my part where the board wouldn't fully start up, just the first 3 beeps, no esc tone.

On the board, the led light lights up solid.

Tested after the fact with a home-made smoke stopper, showed a short.

Removed the ESC's, problem still there.

No boot, not recognized via USB in windows, gets hot.

Tested continuity, there is continuity between ground and 3.3v pad (not good).

I am thinking one of the 3.3v regulators is bad, but I can't find the test to prove this, I only found the test for the schlotter(?) diode, and it is fine.

Can someone help me with how I test with a multimeter which of these two regulators are bad:



I am pretty sure the regulators are the 5 pin part, bottom middle, and the same looking one above a bit and to the right.

Any suggestions are greatly appreciated.

Cheers!

I’m still learning surface mount, and I find the identification of parts to be frustrating to say the least, so take this with a grain of salt.

I think that one at the bottom says “E39” on it. If it does, I don’t think it’s a regulator, I’m pretty sure it’s a INA139NA.
https://lcsc.com/product-detail/Current-...29947.html

The one that says G5K is your 3.3v LDO regulator. It’s a AP2210K-3.3TRG1.
See the data sheet below to view the pin out:
https://datasheet.lcsc.com/lcsc/18072814...176959.pdf

Pin 1 is your voltage in
Pin 5 is your voltage out

You said you’ve got a short to ground, so you don’t really want to do any powered up testing… so I’m not really sure how to test it in circuit. If it were me, I’d remove it, and then see if I still had a short where it’s pin 5 was connected to the board to ground, and I’d do the same to see if there was still a short from where it’s pin 1 was connected to the board to ground.

If I no longer had a short from either of those pins to ground, I’d assume it was the regulator and replace it. If I still had a short, I’d start looking in the direction of which side the short was on (before or after the regulator).

Btw, those first 3 beeps are your esc, if you’re not getting the last two, that’s your flight controller.

Try injecting external 5v supply to the FC via one if the 5v and ground pads to see if that powers up the board. Do the same with 3.3v?

Thanks for the replies,

I will try to do some testing tonight.

I just removed the 3.3 regulator. Short still exists between ground and 3.3v pad. Plugging into usb doesn't cause overheating, but doesn't recognize in betaflight.

Going to take a break and take a closer look tomorrow.

If anyone has any suggestions for testing, please let me know.

Cheers.

If you still have a short between 3.3v pad and ground, then your problem is past the 3.3v regulator.

Might be something simple shorting out, but if I recall correctly, there was a thread about a short past the 3.3v regulator in the past and the consensus was that it was likely a dead mcu.

I could be wrong.