HELP - Crashed / Repaired P4 - All Lights Red

[Laserman532]

Hello Folks, first post here - from Oregon!

I have repaired 1- P4 from a bad crash my son had last year. So I have some experience working on these, last P4 repair still flies (its crash was severe, three motor arms dangling by wires). I bought what appeared to be a very minor crashed P4 off craigslist - shell was only lightly cracked (split at a seam on one arm), motors grinding with grit (so it must have landed upside down in dirt with motors running possibly), landing gear bent (but very minor).

I replace the shell, landing gear and 4 new motors. My solder skills are good, these connections look beautiful. I have not installed landing gear (bottom half of quad). I installed a new battery and turn it on...I get the DJI P4 tone perfectly (as best as I can tell). Battery side arms flash yellow twice, front lights turn on red, battery side lights do a RGY - RGY (a couple of times may be 3 not sure exactly) then all lights stay on solid red. I am trying to get the video I took so I could up load it for everyone to see light pattern. Does anyone have any suggestions what might be the next step in the mean time? ESC Boards (they look like a PITA)?

Thanks for looking at this post.!

 

[Neon Euc]

I could be wrong but have you linked it to the controller? That may be one issue. Or perhaps that the camera is missing or software may need to be flashed again from SD card. Also have you activated again using DJI GO?

 

[Laserman532]

UPDATE- I got app running and linked. First time i tried IMU calibrate it got to 45% then stopped saying temp range is out calibration fail. I built a jig to place a good muffin fan below it...have good airflow to heatsink. heatsink not hot to touch. IMU calibration now stops at 2% (tried two times). I have placed the drone without battery in the refrigerator and will try again in hour.

 

[Laserman532]

after refrigerator for one hour got to 8% and failed. I now have it in the freezer. Is there a temperature sensor that could be faulty? Where is the IMU Board, sounds like if a temp sensor is bad IMU's stop loading and fail.

 

[Neon Euc]

I don't think the refrigerator would have been a good move. The cold will start to form on the wires and electronics and as soon as you take it out, moisture will most likely form. I am hoping I am totally wrong tho

 

[Laserman532]

thank you Neon- yeah it didn't help either way. IMU cal fails between 8% an 16% my record is 36%. Remember this is / was a crashed drone. I get good DJI 7 tone, then solid red. Critical Failure - I figured IMU first before compass. I do not have lower part of shell installed. I have it sitting up right and level on a box with a muffin fan below it...I figured I should be able to get IMU cal without bottom shell on. Thank you for your help. Does anyone know where to buy a IMU card?

 

[Neon Euc]

I know a few people who may know

@msinger
@withthebirds
@captainmilehigh

Hopefully these guys and a few more will be able to chime in

 

[Neon Euc]

Also check out a site called Ali express as they do lots of phantom spare parts on there at a great price

 

[Laserman532]

UPDATE - thinking that it was taking long time to transmit data to no antenna, I installed landing gear and connected antenna and compass (trying not to snap shell together). ran test IMU fail 68%. Thinking it needed some cooling I installed broken gimbal part with fan on it. repeat test (fan turned on at power up) fail at 21%. My experience is THIS QUAD does not like fan on when doing IMU cal.

 

[Laserman532]

removed gimbal fan ran test two more times - IMU cal fail at 58% and 63%. each IMU goes up by 1% each in steps very slowly. There is a tiny dot next to IMU1...there is no tiny dot next to IMU2...does it sound like this IMU card is toast? Thanks for anyone who wants to chime in. I looked on aliexpress and they did not have a PCB. Does anyone out there know where I can get one? THANKS!

 

[Neon Euc]

Not sure if this may be it. I am using the app at the mo so have no option to share link

 

[Laserman532]

Thanks for the link...does anyone know if that is where the IMU circuity is located? I don't know what that board does. I know what the ESC boards are and the PS board is but not this one.

 

[Neon Euc]

Also saw this one... Forgot to ask if its the pro version you have

 

[Neon Euc]

Yet again sorry for no link as I am not on the laptop but type in what it says and it should come up

 

[Neon Euc]

Type this store name on eBay rod. He has lots of spare parts. And may also know the part your looking for. Hope this helps a great deal.

 

[Neon Euc]

Also I am from London, England so a lot of your local eBay sellers may not appear on mine and vice versa. Also I am still learning about the drones too but hope I helped you get started in some way [emoji4][emoji4]

 

[Goof]

Never, EVER run radio gear like this without an antenna or shorting resistor equipped to protect the radio circuit. Your original problem was likely the drone complaining that it couldn't initialise either compass circuit, since they weren't connected to the power distribution board. It could've also been complaining about the lack of the camera boards, these are important to the drone, since they cool the heatsink on the main board. Now however you have likely fried the main board and will need a replacement.

For future repair jobs, if you need to run the drone with the lower case off, dismantle an old set of landing gear and pull the antenna/compass boards out. You can connect both compasses + the four antenna wires and then lie the boards alongside the drone out of the way while you perform whatever testing you need to do with the main board running.

 

[Laserman532]

UPDATE - I was able to calibrate compass successfully. the IMU calibration stops at 65% when NO fan gimbal is installed and stops at 2 to 8% with fan gimbal installed. Which board is the IMU sensor circuit on? Is that what you are calling a main board? I see the one add for Ebay. Where else can I buy one of these boards as the ones on eBay may not work. Add states - "NO WARRANTY expressed or implied"

 

[Goof]

Main board is the one the heatsink is on, where the antennas plug into.

IIRC, the IMU is on the tiny rubber mounted FLT_CTL board. If you find one of those you could maybe try that instead...

As far as warranty goes, unless you get one through DJI store I'm not sure too many places offer a warranty. The reason these boards are cheaper than the DJI store is because they're pulled from otherwise working craft and sold off.

 

[Laserman532]

I have ordered a flight controller board off of eBay - 78.00 from a US reputable dealer. Supposed to be here next week...my question...should I upgrade the firmware? I assume it is located on this board?