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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You are right about that...

I had proposed to randy to put a wire 3.3 to A0 and thus to survey or record the 3.3 as is done for 5v

I wonder how many of you with blown 3.3V regulator  did update of PPm encoder, maybe that's connection....I am no expert this just came to my mind and I share it.... 


I really don't know how or when my 3.3v regulator failed but I didn't do anything with PPM encoder.  I just noticed it when testing the beta of AC 3.1.  

I DID update my PPM encoder and have checked my regulator with a reading of 3.3 volts. Not saying it couldn't be the update causing the issue as some folks may have inadvertently shorted something in the process.

I did update my PPM encoder recently and my 3.3v reg. was fine after the upgrade...

Randy, et al,

I too believe I have blown out my 3.3 volt regulator.  After upgrading AC 3.1 from 3.0.1 on my APM 2.5, I immediately noticed the choppy HUD as well as gyro not healthy alerts.  Upon testing the IC2 port I did notice 4.9 volts rather than 3.3.  To my knowledge, I do NOT have a PPM encoder unless it is internal to the APM 2.5.  I know I do not have an external PPM encoder similar to the unit being offered with the PixHawk.

That said, I have ordered the correct regulator from Digi-Key as well as treated myself to a shiny new (backordered) PixHawk and GPS+ Mag combo.  I did not order the PPM encoder because I use a Spektrum AR8000 Rx (is that okay?).  In the event that I cannot successfully replace the regulator what is a gyro-less APM 2.5 still good for? AruduRover?

Could someone that has successfully replaced their own 3.3 volt regulator please post a detailed (w/ pics) best practices step-by-step of the procedure that would be greatly appreciated!

Thank you in advance, and Happy New Year!


Mike, there are many pictures in this thread about 3.3v reg. replacement. I don't think there is one complete post that shows how to do it step-by-step but all the info you need will be somewhere in the previous pages. You just need to look through them:)

Thanks Alex, I will poke around more. I was wondering if one soldering method might be easier than an another. I have seen several iterations. I am probably overthi

What's easy about that?  Why would we be expected to repair our own defective hardware?  Some people don't have soldering irons or soldering stations.  That's at least $25 - $50 worth of tools right there.Even if you do have the right equipment you run the risk of damaging your APM trying to remove and replace the regulator.  It's not 2 soldering places, it's at least 7.  5 on the old and 2 on the new. Most novices will probably destroy the board just removing the old one. And even if you get it fixed, you've got a product that is now rigged like a Christmas tree (not like it wasn't before).

3DR should be fixing these, not telling the people who spent $150 on their defective product to solder some regulator on there for them.  They fixed their defective software and now it reveals defective hardware. This is clearly a widespread problem. I don't mind paying for the shipping, it's better than frying my APM.

Many of us are here DIYers. Heck the name is on the website:)

We enjoy repairing stuff to some extend. I love fixing stuff on my own. This gives me pleasure. 

However, there will be some (like Josh) and they may not have the right equipment plus they may not want to fix the hardware they paid for especially if it is not their fault. I think those people should have every right to complain. 

This said, I totally understand your complaint Josh. And I don't think anyone can blame you for this frustration. 

My personal understanding is that 3DR would have taken some responsibility and action for this matter if they knew what the real cause was. They just don't know. And I think we won't be able to see a definitive action till they find what exactly is causing these regulators to go bad.



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