Weird motor/mainboard issue.

[Xelodaki]

Hey guys!

I bought used Phantom 3 Pro in hopes that i could fix it. It has weird problem with the motor rpm's. When using the lift-off feature on phone, 1-2 of the motors spins erratically, like up and down in rpm's, almost impossible to get the drone into hover/fly. Then i tested the drone without lift-off, manually controlling motor's rpm's with controller. Motor's spins nicely when the propeller's aren't attached, but with propeller's it becomes unstable. Two of the wing's have cracks under the motors.

Does this problem have something to do with the motor's/mainboard or something else?

Thanks

 

[quaddamage]

While it's hard to tell for sure, motor and ESC issues are typically found and announced by the drone (the app message is usually "ESC Status Error").

So while it could be motor os ESC, there's considerable chance it's IMU or internal connections somewhere.
There are people here good at analyzing logs, you could try that.

 

[RodPad]

Welcome to the forum!

Picture of the cracks would be great!

Rod ..

 

[Xelodaki]

Welcome to the forum!

Picture of the cracks would be great!

Rod ..

Thank you!!

Here is picture of the cracks.

 

[Xelodaki]

While it's hard to tell for sure, motor and ESC issues are typically found and announced by the drone (the app message is usually "ESC Status Error").

So while it could be motor os ESC, there's considerable chance it's IMU or internal connections somewhere.
There are people here good at analyzing logs, you could try that.

Is there any obvious place to look for? I already have the drone shell open.

 

[quaddamage]

Is there any obvious place to look for? I already have the drone shell open.

The FC is soldered in on a daughterboard. The connections of said daughterboard can sometimes tear on hard landing. Hard to spot if that is the case though, tear on solder is barely visible.

For IMU - it would be hard to spot anything by just looking, and there's a rubber-like glue keeping IMU connector in place, so not sure if it's worth disconnecting.

For ESC - if you have a multimeter, you could check resistances on all MOSFETs - maybe there's one which stands out.

 

[Xelodaki]

The FC is soldered in on a daughterboard. The connections of said daughterboard can sometimes tear on hard landing. Hard to spot if that is the case though, tear on solder is barely visible.

For IMU - it would be hard to spot anything by just looking, and there's a rubber-like glue keeping IMU connector in place, so not sure if it's worth disconnecting.

For ESC - if you have a multimeter, you could check resistances on all MOSFETs - maybe there's one which stands out.

Ive been lookin the mainboard through with a digital microscope, can't find anything that stands out, also very hard to get clear image because of the glossy coating on the motherboard.
One wire on the camera connector is almost broken, but i suspect i damaged it when breaking into the shell and i would image if it was broken earlier it wouldn't affect flight?

I'll nect measure the mosfet's and write you back about it.

Also greetings from Finland and thanks for helping! I really hope i could get this drone fixed!

 

[Xelodaki]

The FC is soldered in on a daughterboard. The connections of said daughterboard can sometimes tear on hard landing. Hard to spot if that is the case though, tear on solder is barely visible.

For IMU - it would be hard to spot anything by just looking, and there's a rubber-like glue keeping IMU connector in place, so not sure if it's worth disconnecting.

For ESC - if you have a multimeter, you could check resistances on all MOSFETs - maybe there's one which stands out.

Yeah so i measured all mosfets, no faults

 

[quaddamage]

Yeah so i measured all mosfets, no faults

Download the DAT log and share. Hopefully someone will take a look.

 

[Xelodaki]

Here is link for the 3 data logs when i first time tried to fly it; DAT log PH3P - Google Drive

Download the DAT log and share. Hopefully someone will take a look.

 

[Capt KO]

Sounds like a blast from the past. Cracks under P3 motors and rpm problems. I used to either replace the shells or place motor guards (preferred metal over plastic) under all 4 motors. Anyways, not doing that anymore so good luck

 

[Xelodaki]

Sounds like a blast from the past. Cracks under P3 motors and rpm problems. I used to either replace the shells or place motor guards (preferred metal over plastic) under all 4 motors. Anyways, not doing that anymore so good luck

Do you think that the cracks causes rpm problems? I epoxy glued them yesterday, not tested yet. Quick Google search and i can also order metal reinforcements for it.

 

[Xelodaki]

Just went for test flight with glued arms, no effect, problem is still there. Calibrated compass and IMU, ok no errors.
Tested the drone with propellers attached on my table and holding the drone down, and there is no rpm problem, only occurs when trying to fly it and on uneven surface (ofcourse it tries to straighten itself)

 

[Capt KO]

If the motor is pinched or twisted , it's possible. Anyways, I put metal motor supports on all the P3 models, cracks or not, that I flipped in old days. I had so many spare dones back then that switching parts for diagnostic wasn't a problem

 

[Xelodaki]

Yeah Well i don't have any spares.

 

[captainmilehigh]

Yeah Well i don't have any spares.

Maybe try a new set of props? Even though OEM props are 'true' when made, I still balance all my props. If you have aftermarket props, they might be so far out of spec they are causing issues.

 

[Capt KO]

Anyways, just don't spend much, P3 series fairly inexpensive nowadays. Maybe cheap enough to buy another spare. Tiny drones rule nowadays but I still love my big old Phantoms. The P3/P4 Phantoms can carry over 1lb of weight, something the Mavics and other little drones will never be able to do. To me that's their main value as new drones that can carry that much weight will cost many THOUSAND$. And it comes with an awsome camera to boot.
Good luck

 

[Xelodaki]

Maybe try a new set of props? Even though OEM props are 'true' when made, I still balance all my props. If you have aftermarket props, they might be so far out of spec they are causing issues.

The drone came with like 4 sets of props. Don't know if they are OEM or not. Props that i put on it were New.

 

[Capt KO]

The drone came with like 4 sets of props. Don't know if they are OEM or not. Props that i put on it were New.

All DJI OEM props have the DJI logo embossed in small print on the blades. Off brand props are NOT recommended and are prone to failure. I've thrown away many a new set that came with used drones I purchased, they're a recipe for disaster. I even have a video of new 3rd party props flying off my drone on takeoff.

 

[captainmilehigh]

All DJI OEM props have the DJI logo in small print on the blades. Off brand props are NOT recommended and prone to failure. I've thrown away many a new set that came with used drones i purchased, they're a recipe for disaster.

.......and if a prop fails, gravity takes over.......and we all know that outcome.