This is a discussion re the bad Accel, Gyro and Baro values that we're seeing with ArduCopter-3.1.  The increase in the SPI bus speed from 500khz to 8Mhz has exposed a hardware problem on some boards.  That hardware problem is that the 3.3V regulator has been blown so all sensors are running at 5V instead of the intended 3.3V.


How have these regulators been burnt out?

  • Attaching a radio receiver or MinimOSD to the APM while the APM is only powered through the USB (see video below)

  • Some clone boards seem to come from the factory with blown regulators.  3DR boards might also come with blown regulators although they do a specific check of the regulator as part of the regular QA process.
  • It is not (as far as we know) actually caused by the AC3.1 software itself, it just exposes the problem.  You could prove this to yourself by checking the 3.3V regulator (see video above) before and after the upgrade.


How can we fix the regulator?

Option #1:  If it's a new board (so that it's less likely you burned it out yourself) you could report the problem to the retailer that sold you the board and ask for an replacement.  If it's 3DR it's called an "RMA".

Option #2: if you're handy with a soldering iron you can replace the regulator yourself.  On the APM2.5.2 (and higher) boards it's not that difficult.  On the APM2.5 it's far more difficult.

For APM2.5.2 : TPS79133DBVR

For APM 2.5: MIC5219-3.3YML TR

How can I stop it from happening again?

Do not connect any devices such as a radio receiver, MinimOSD, GPS, etc while the APM is powered especially while powered only through the USB cable.

Attaching a 100uF capacitor across any of the APM's radio input's 5V and GND pins will stop the regulator from being blown by plugging in a receiver.  video here!

There are very few reports of regulators being blown twice and no reports of it ever failing in flight.


Below are some graphs of the types of values that we are seeing on these boards.

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Is there a specific type of soldering iron tip suggested?  If so, can you please point me in the right direction?



I also have the same voltage regulator casualty but without a 3.3V output - bought the APM 2.5.2 board from China.

The APM is being powered by an ESC (at the APM input, only 5V & GND connected to the board from ESC). We got the board to work with our setup initially, got it to arm/disarm with the motors. But in some kind of simultaneous combination with the input voltage, with the USB connected/disconnected and/or APM board powered on – all of a sudden, we couldn’t get connected to Mavlink. I did some troubleshooting and found that the voltage regulator did not have a 3.3V output.

Also, I’ve noticed that if the USB is connected to the board, with no battery connected, it seemed like the USB is making/breaking when we just toggle the BEC power connection to the APM. The PC gives a sound alert that the USB port comes and goes. Weird.

I'm going to replace the part this week and repeat our setup. Still need to figure out the root cause for such failure to prevent it to happen again.

pour une fois qu on fait du diy made in france j en profie pour poster le liens lol

it s the main reason why i will never buy something on their compagny..

theirs hardware are ofter crapy design so i prefer to buy vrbrain than their new suspicious pixhawk.

so yes i love arducopter but one thing i dislike is the poor conception hardware

Yeah, and their powerdesign was always faulty within the APM2.x line now a killerpoke software reveals the next weak point: the 3.3V regulator. Where is the red warning sign in the shop to protect users from crashing?? That pixhawk half baked hardware reads "Redundant power supply inputs and automatic failover" maybe it's time to implement 3 other chips to watch each other if the other 2 fail.

People get criticized why replacing the 100mA reg with a 1A type - well I ask back: why not replace it with a 100A type to see the faulty wires actually burn out.

Just look at the old freeflight board from goodluckbuy and its' powerdesign that would supply a city with 3.3V (just joking)...

I have successfully replace the 3.3V regulator in my original APM 2.5 that got a "no dataflash error" while connected only with usb cable .

Soldering was quite simple removing the faulty component,  a bit more  difficult.

I put a drop of tin solder that touch the three pins while lifting  the side of the regulator with a thin blade (it must be thin to not cool the tin solder  drop) and repeat the same on the other two pins.

I use tin-lead solder because of lower temperature needed.

nicely done!

Well, with an attached picture or two, I guess you would be the first one showing reg. replacement pictures on original APM 2.5:)

Thank you!

I am happy to report that we have one more APM 2.5.2 back in service after a successful regulator transplant.

Thank you for the assistance!


I replaced one too. My method involved using an X-Acto knife and carefully, gently making cuts across the legs of the old regulator right next to the chip until I had cut the regulator free, leaving the five legs still attached to the board. Then it was a simple matter of using the tiny tipped soldering iron to "wipe" the legs off the board, finishing it up with some solder wick to clean the pads of excess solder. Then I applied a quick, thin layer of solder to the pads, keeping it very thin. I put some solder paste on each pad. Added the new regulator, holding it in place with a pair of tweezers. Tinned the iron with a tiny bit of solder and touched it to one leg of the regulator which locked it down. Then, just went around it touching the iron to each remaining leg and the solder simply flowed and made each connection. Q-Tip and Alcohol cleaned up the paste.  I used the knife method to remove the regulator so I didn't risk damaging the board by pulling a trace loose, overheating or loosening the capacitors in close proximity to the regulator. I didn't do any pictures, sorry. 



It now appears that I have lost my uBlox GPS module after transplanting the 3.3v regulator.  It no longer powers up.  Is there a possibility that I could have damaged the board while soldering on the new regulator?

I have log files but I don't know what I should be looking for.  I have tested both GPS ports.  When I do a CLI based test of the GPS all I get in return are "................................" with no data.

At least my HUD has stopped wobbling.





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