Strange Motor Sound - ESC Problem?

[my414]

I just got a refurbished Typhoon H a few days ago and took it out for its first flight. Upon starting up the motors I noticed motor 5 (directly to the right) was acting odd. It attempted to spin for about 10 seconds then I got a warning and it went into 5 motor mode. I reset everything and tried again, this time it started up but it was making an awful noise. I flew it up about 10 feet and I flew in all directions for about a minute. The noise did not go away. I landed and brought it inside and noticed the motor was VERY hot, almost too hot to take the prop off.

I connected it to my computer and used the GUI to power each motor and once again motor 5 acted strangely. It would take about 5 times longer to get up to speed and not sound 100% right.

I have a "spare" Typhoon H that was crashed into a tree during RTH (long story, my fault), so I decided I would remove motor 5 arm since I know it worked fine and put it on my non-crashed one. I was sure that this would fix the problem but it still sounds and acts the same way.

My conclusion is that it must be the main board and that it made it past Q&A since everything powers up fine.
I attached a video of it starting up. What do you guys think? I will be on the phone with Yuneec support on Monday.

 

[Steve Carr]

All indications certainly show something wrong with that motor circuit. Either the ESC or motor. Since you replaced the motor that only leave the main board.

 

[CraigCam]

All indications certainly show something wrong with that motor circuit. Either the ESC or motor. Since you replaced the motor that only leave the main board.

A bad ESC will flip flop the motor even and after a few seconds go into 5 motor mode. Unfortunately, it’s all surface mount and micro sized so you can’t replace them. It does require a new main motor board. I found a good one from a fellow forum member for a good price. Carolina Dronz will have them sometimes also when they part out a TH.

The best way to check a motor in my opinion is to hand bat around between each motor with as consistent a blow as you can. Good motors make a nice whine with no chatter and stop evenly as the rotation force goes below the magnets hold. One bit of gravel (or piece of metal/iron)in between the coils and shroud will cause the motor to over work which in turn can burn up the ESC. I also don’t trust any motor that suddenly stopped by a crash or prop strike as that seems to damage some of the magnets and you get a motor with “gaps” in its power. This in turn makes everything else work harder to compensate for the weaker motor and leads to other problems in flight like quicker battery draw and faulty stick response.