IMU shield repair advice needed

Hi everyone!

I had a nasty crash last weekend. (More to follow…) Now my IMU shield needs some repair :) Fortunately it still boots up and the imu test results make some sense. Here's a pic of what has gone missing on the board plus my thoughts about how and what to replace:


There are two things I need your advice about. 

A - missing caps:

My board is of a different revision than the one documented in the wiki. On the back side it says " HOTEL1.0" and "8/19/2010". Comparing it to the schematics on the wiki I think the missing components are C23 and C25 with a value of 0.1uF respectively. I'm only an amateur with electronics, so I would be glad if someone with more insight or access to the corresponding schematic could check, if my assumptions are correct.

B - flight mode switch:

There's this new "3x return" thing to enter CLI mode. Does this also work with the older hardware revisions or only with the new APM 2.0? If it actually works with my hardware I could just hardwire it to flight mode and forget about the hardware switch, right?


In general, would you advise to try repairs and fully trust the autopilot again, or would you consider it unsafe to use it after this kind of damage? Obviously, I don't intend to fly a commercial airliner with it :)


Thanks a lot for helping me out!



Links to schematics in the wiki (wrong revision):



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  • Thanks Marcos and Zach for your replies.

    I replaced the relevant components and ran all tests multiple times. Unfortunately it doesn't start up reliably, gyro calibration sometimes just does not happen. It makes a difference if I put pressure on the boards in a certain spot. This could indeed be an indicator for cold/broken solder joints or traces. In CLI mode, Calibration always works if started manually. 

    I will no longer use it on a airplane, but it will sure come in handy as permanent HIL simulation device.

    Oh well, it's just a toy after all... :)

  • It depends on your skills, from the sound of it I would say you should give it a shot on repairing, make sure all the test work out on the bench and just be cautious if you ever fly with it. But almost always worth the shot

  • hi Chris,

    looking at the schematics, you can find Hotel V1.0 here:

    you are right, both, c23 and c25 are the ones, and they are 0.1uF. With c25, you are lucky, its seems to be the analog filter for X axis sensors, so if you desolder de Jumper 20, it would be ignored.

    For the c23,i'm not sure, but i think its a filter for the fti chip power to avoid voltage peaks from usb or wherever, so if i´m rigth, it could work withoth the Condenser but it would be very dangerous for the chip and you finally  will burn it.

    If you are going to try to resolder it, try not to use a simple iron solder, find a solder station with a thin tip. There is a post about gyros failure were Chris talk about 325º K to reflux the chips. you got to be fine or you could fry another think.

    About the cli sw, i think the 3 enter feature is for the APM2, that has not a cli sw, i don't think it would work in your board, but still don´t sure. If you don´t find exactly the same sw you could allways put three pieces of wires solder to the board pins and that wires to a any size two states sw.

    About relaying on it again, you got a lot of tools to test and test and even simulate. Once you are sure it works, test it again. And start flying with care. A flux joint could be fisured for example and work on your desk but not under motors vibrations.

    Good luck with that.

    Marcos Rivera.

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