Hello forum,

finally got my first 5 inch second hand which was in pretty rough shape and came right out of a mud mask . After cleaning and setting (almost) everything up I'm now stuck, what feels right in front of the fnish line.

Three out of four motors are stuttering and producing a scraping sound as like as they had sand inside. So I already opened up one of the scratchy sounded motors and the only good one for comparision though they had some dirt inside motor didn't get better after some compressed air treatment.

After already watching a lot of videos and reading on the internet most people suggest to swap around motors and conclude from that if it is maybe the ESC or the motor. Though I could do that I could't fix it at the moment anyway since I'm in holidays resp. at family and there is nothing I could do about it. So my only hope would be, that there is something I forgot to set-up or configure.... 

Video:
https://www.mediafire.com/file/l156cbih9...7.mp4/file

As you can see Motor 2 (front-right) is doing well while the others are first scratching, twitching and jerking around and then getting turned off completely.
I can address all 4 motors from Betaflight. Also I can see all ESCs from BLHeli-Configurator (while from BLHeli-Suit I don't manage to connect at all, however guess that's just my or my PC's fault) BLHeli-Configurator is fine and I can see that 2 of 4 ESC's are in reverse.
I would have tried to update the firmware of the kwad since Betaflight is still 3.5.3 but I also cannot find the Firmware of the GEPRC Mark 2 on the webpage of geprc.com maybe somebody has a hint on this as well?
Also tried to calibrate the motors in the motor tab of Bataflight though I'm not sure it was successful. Though I heard the second special meleodie for "low output" I think i miss the first/starting melodie for "high output".



In the attached screenshot you can see the motor output of 50% throttle (coming from 0% throttle).

   

So I'm asking for your input and hoping for "this-hidden-switch" I forgot to tick. Thanks in advance
Wasp

If cleaning the motors did not help spin them up freely then something else is at play and the next suspect is the ESC. Since you say blheli is able to detect the 4 motors then its the MOSFETs on the ESC which are faulty.

Can you try and swap a bad motor over to the good one to see if the behavior changes? Don’t run this for too long, we just want to know if its the motor or the FETs.

(22-Apr-2022, 11:45 PM)kafie1980 Wrote: Can you try and swap a bad motor over to the good one to see if the behavior changes?

Since I have no good tools here nor anything more sufisticated my actually question was if there is something *else* I could try what I haven't consisidered yet on the software side since I'm still pretty new to the hobby and for sure for 5 inch. I admit my first post was a bit messy since it was the last thing before falling into bed.

So far I've:

• checked for a update of Betaflight from v3.5.3 but I guess I need one for `OmnibusF4SD` while in Betaflight there is only the one without `...SD`.#
  •  On the GepRC webpage I couldn't find any firmware or anything else mroe than a pretty poor quickstart-guide for the `GepRC Mark2` at I find a bit sad. Anybody has another source maybe?
    
• tried to clean a jerky motor but without any improvement
  
• visually inspected the ESC but cannot see any obvious demage (no chipping, no burns).
  
• tried to calibrate the motors by putting them to max and then to min in the Betaflight configurator. However I'm not 100% certain it worked out becauseI only noticed the special "melody" for minimum motor output but not the starting "melody" for maximum motor output.
  
• (While everything still connected: ) I've check for every individual motor the continuity between the three wires. They seem all fine (and all the same including the only working M2) -- contenuity available.
  
• (While everything still connected: ) I've checked for short circuit from the main power pads +/- to every motor wire plus between +/- itself. Seems fine -- no (full) short. (Though I have a low leakage due to the mosfets. But again, also the same for *every* motor including the working M2.)
  

Though there is of course the chance of a none obvious demage but at least from my current perspective I find it unlikely, especially for 3/4 motors. So is there something on the software side I maybe can test/check first for what is maybe a common mistake when having jerky motors? Some misconfiguration? What can I check for?

Kindly KremerFPV uploaded the default config of the GEP-Mark-2 though today it's a pretty old version from february 2018 for Betaflight 3.2.5 (Link: https://textuploader.com/dvww9)
I checked for differences to my exported version but coulnd't see anything magnificent. Without actually knowing what I see here, this part looks a little weird since it is set to 0 and 'gyro_32khz_hardware_lpf' didn't exist in the old one -- but maybe it came with a Betaflight update(?):

"My" full config here: https://textuploader.com/t1qi5

Also managed to connect via BLHeliSuite -- if you know how, it's actually pretty easy ;-)

Here are some screenshots out of BLHeliSuite in the hope it helps somebody to help me:
   
   
   

You’ve mentioned mud and 3x scratchy sounding twitching motors.

I wish that I could tell you that there is a setting you could change to make all motors work- but honestly, it sounds like either 3 of your motors are toast, or three of your esc outputs are toast, or both. There’s not really a way to test that without swapping the known good motor to the other positions.

If this thing crashed the wrong way and had 3 of 4 motors caught up in mud or weeds or tree limbs, and the previous owner kept trying to power out of it- they could have very easily killed the bits that don’t work.

Scratchy motors can be bad bearings- but I wouldn’t bother replacing them until I tested each motor.

I haven’t tried testing dead motors with just a multimeter- I have an lcr/esr meter and I use that to check each motor when I think one might be dead- because continuity between two motor wires doesn’t tell you much if those two wires burned off their insulation and are shorting out.

Thank you for your support.

Once I already bought a (small) drone and it was behaving weird. In the end it tunred out the former owner just installed a similar but overwall wrong firmware. Setting it back to factory settings/fw fixed everything. So also for this one I was still looking for something "stupid" before torture it with this bad soldering iron here. For exmaple:

• generally some wrong setting with the motors (in extreme set to 3 motors instead of 4)
  
• wrong firmware (type -- omnibusf7 or omnibusf4 instead of omnibusf4SD...)
  
• wrong BLHeli settings or fw (like using blheli32 instead of blheli_s)
  
• wrong frequenz for motors ....
  
  
• .. something I'm not even aware of, so that's why I ask here
  

However it seems I just have to swap the motors. Though whatever I find it wouldn't elimenate any of the above potential problems. Still the firmware could still send some crap to the esc/motors due to missconfiguration while the esc/motors on there own without fault for exmaple, isn't it?

I'm still confused what I see in the picture of the motor tab from the first post. I'll add video later...

i like to second, there is "no" software wise option can cause this, you need to do the motorswitch. changing betaflight software cause of an issue is not a good way for troubleshooting, it makes it more difficult to figure out hardware issues by changing the software.

truly shuttering motors sounds like a diyng esc, but either 3 out of 4 esc or motors can die in a crash. even both could die together in one crash

check the connection between esc and fc, the wires of the motors and the capacitator leads, but how you described the issue, there isnt much hope to find the issue there...
the firmware doesnt change its work, if it worked well befor, there is no hope for a "wrong setting"

Swapped two motors. Have terrible solder joins now, but motors seems fine. Problem stayed with the ESC-motor-pad.

You might need a new ESC as it seems the MOSFETS are bad causing the stuttering of motors.

For good solder joints you need flux and leaded solder. Best $20 you will spend even if you buy TBS solder and flux which is what I use due to easy availability.

(24-Apr-2022, 11:21 AM)hugnosed_bat Wrote: check the connection between esc and fc (...)

It's a pretty sturdy"fixed" pin-connector.

(24-Apr-2022, 11:21 AM)hugnosed_bat Wrote: if it worked well befor[e], there is no hope for a "wrong setting"

Well, I bought it second hand. I have no idea. But considering from the mud inside and assumig the former owner didn't just through it into a mud puddle: some point in time before it was able to fly. ;-)
But Maybe the mud is not the cause, just a considence and s/he just f*** up the firmware...?

Considering the overall shape, the ESC looks pretty okay to me, though I know it doesn't have to be visual:
   
   

So actually I can choose between sending this crap back, which I'm pretty tempted to, or buying a new (4-in-1) ESC; or at least probes to check for the faulty mosfets...

Finally had a look into it since I'm back home and stumbled over a video which pretty much reassambles my issue:
https://youtu.be/csCBMF8P3qg?t=120

He solves it by setting `min_command` (which, in contrast to Cleanflight, in Betaflight I could only find via CLI), `min_throttle` and more importantly by calibrating the ESC.
Though I followed along the procedure already before -- and just did it again multiple times -- I never get any real acknowledgement of the start of the esc calibration process by sound/motors. Which makes me wonder if I ever did it for real.

1. What could lead to not getting the melody/process for esc configuration started despite having throttle up in the motors tab of Betaflight Configurator?
   
2. How could I do the same without Betaflight Configurator? (Tried to do the same via the transmittor only as like as seen in the this video here https://youtu.be/KV0DzOQDk8M?t=82 but without any success too. -- Also removed pre-arm but without any avail.)
   

I understand you have a BLHELI_S 4in1 ESC?

If you are flying DShot protocol then you do not need to worry about ESC calibration as its no longer required.