It's a long story that I will try to summarize. The latest revision of the magnetometer that had some design improvements including making it easier to manufacture to boost production using the pick and place machine, but that also came with a weird issue. 

When I was developing the APM Oilpan we had some noise issues on the 3.3V line caused by a missing 200K resistor on the Voltage Reference pin on the 5V side of the I2C translator (obviously this board never saw the light), if you don't populate this resistor it will introduce terrible noise on the line and cause the analog sensors to fail, this bug was found by Jose Julio (Thanks!). 


A curious thing is that the first version of the magnetometer didn't have this resistor (it worked fine anyway), in the second revision i tried to do the right thing and follow what the datasheet suggested so I added the 200K resistor (same that caused terrible issues on the Oilpan because we didn't use it), expecting some improvement. 


When the boards arrived from the fab, we assemble some and they appeared to be fine, Cindy (our testing lady) added the observation that the sensors were slightly noisier, but we didn't listen (Sorry Cindy!). For the pressure of months of long waits we just released the boards. In just matter of days we received tons of complains.   


After days trying to solve the problem we finally discover that the 200K was the issue. The 2nd issue we have discovered but is not critical is that the voltage regulator will not perform well if you don't suck enough current from it, the magnetometer uses very, very low power and the best practice to solve this is to add a 200 ohms resistor from the 3.3V to GND to add enough load to it (Thanks to Nathan Siedle for this trick), we are not doing this right now, so you will see a power supply output of 3.7V, but the performance is perfect. 


All new boards have this fix, but for those who already got affected boards I would like to give a sincere apology to all our custumers and I would like to offer two resolutions to this problem:

1.- Send it back and we will repair it for you. We will cover all the shipping expenses. Please contact custumer support for more info: help[@] 


2.-Repair it yourself (DIY) quickly and safely by following the following instructions.


NOTE: Before you repair your board, check if your board has a resistor marked "204". This means it has not been fixed (see the first two photos of the repair steps for reference), and if you see instead a resistor marked "0" your board is fine.

If you choose to repair it yourself and something gets messed up, you cannot then return the board. If you are unwilling to take this risk or are feeling a little uncertain about your soldering ability, do not do this. Just return the board for replacement.






















1- Locate the 200k resistor, it is marked with "204."






















2- With a soldering iron, heat either of the resistor's solder points
and wait a few seconds for the heat to reach both solder points. Weak solder irons may not work very well. 























3- Without applying too much force as no not damage the pads, gently
nudge the resistor with the tip of the soldering iron. 























4-The resistor

should stick to the tip, so just lift the tip off the board to remove
the resistor.






















5- Make sure you the pad are still there. 






















6- To create the solder bridge place the tip of the soldering iron
over both pads and apply enough solder to brigde the pads.














































7- If the solder ball is touching both pads then your are done. 

Views: 2778

Comment by Franck on January 17, 2011 at 4:41am

Thanks Chris!

I'll try that, I didn't see it.


Comment by Max Nippard on January 18, 2011 at 4:13am

If your outside the US and don't want to post your board back visit your local hackerspace.

Anyone in Sydney is welcome to visit the local hackerspace where we have all the tools and experienced solderers to do this modification or guide you to do it. 

I'm sure all other hackerspaces would also welcome visitors wanting soldering help.


Comment by emile on January 18, 2011 at 5:12am

Hello, after braking a pad on the 3.3v regulator I was wondering if anyone could help me understand if this pad is actually used or not. I saw the schematics, but I'm totally numb in reading it.... so the pad I broke is marked BP on the schematics. If I don't connect such pin, would things still work? It looks like it goes nowhere and it is not marked OUT... so maybe I'm still lucky.

Help appreciated,


Comment by Sam Kelly on January 18, 2011 at 9:30am
@ emile: The BP pin on the 3.3V regulator is not used in this case. But I have to ask, what were you doing to the regulator? it's not mentioned in the instructions above.
Comment by Lee on January 18, 2011 at 9:59am
Ughhhhh!! Damn! I hate soldering. Have to order a new board!!!!! I think I ruined mine....
Comment by emile on January 18, 2011 at 11:06am

I had the board with the two mounting areas (and big IC chip). I had to cut off both to solder it on top of the IMU. In cutting it near the 3.3v I broke the pad... this was my first magneto and I thought it was broken. Then I bought another two and the first stopped working after a short period, the second never worked. I am shipping the latter for RMA, but after seeing the schematics, i thought I could use the regulator of one of the others to make the first go...


Comment by Gary H on January 18, 2011 at 5:16pm

Can we expect all boards shipping after this posted date (January 12th) to be modded already thus saving many the task of doing so since it appears to be a remedy to a design flaw?



3D Robotics
Comment by Chris Anderson on January 18, 2011 at 6:41pm
Gary, yes. All boards shipped out after this notification have the fix.
Comment by Gary H on January 18, 2011 at 7:08pm
The reason I ask is that the board I just did receive today did not have the fix in place.

3D Robotics
Comment by Chris Anderson on January 18, 2011 at 7:20pm
Gary: When was it shipped?


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