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One of the motors turn on as soon as battery is plugged in?!

SJLPHI

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Hello,

I have two tellos. One was always a bit "off" and I deemed "defective" because the suppliers was dishonest and it came with an extra screw stuck to the motor, and another one that always flew well.

I call the defective drone the "A" drone. It was my first Tello and I bought it "new" but it obviously had signs of refurbishments and in Switzerland return policy isn't as liberating as in Canada or U.S. so I took the loss and kept it.

My A drone has been flying for about 100 hours, and had 6 motorsreplacements. I now have the weirdest problem. Since the last flight, one of the motors turn on immediately as soon as I plug in a battery!

Just before that, I switched out one motor that was heating up unusually and the batteries ran out in ~5 minutes instead of near average ~13 minutes.

I checked the circuits many times over and there is nothing from the PCB to motor contact that is shorted. There is no analog contact that should turn the motor on when I plug in the battery. The flight processor has been under some intensive heat but could that actually cause a malfunction like this?

I am grounding my A drone for now but I have a really hard time figuring out what's wrong with it. Now the camera doesn't work anymore and the drone barely turns on. It seems like A drone is finally toast and time for B drone to fly again.

Any clue on how to repair my A drone? For now, I've salvaged all motors, and I will take out the PCB entirely to work on it.
 
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Since the last flight, one of the motors turn on immediately as soon as I plug in a battery!
As it is unlikely to be a software problem I would guess at a short circuit driver transistor, or a similar hardware problem. Unless you are a real electronics enthusiast I would think that the motherboard is toast. You can probably reclaim the camera and infra-red module if needed.
 
As it is unlikely to be a software problem I would guess at a short circuit driver transistor, or a similar hardware problem. Unless you are a real electronics enthusiast I would think that the motherboard is toast. You can probably reclaim the camera and infra-red module if needed.

I actually have been recently practicing soldering small boards and have a bag full of transistors in similar size as seen on the Tello board. Thanks for the suggestion.
 
8846QM active chip responsible for power supply I have not thoroughly examined the pcb
but you could try to replace it
 
It will take... a lot.... of practice soldering before I can replace that.
 
Sweet! I don't know how you know this but I will certainly try.

I'm not 100% sure if this is the cause of your problem ... but this cips if you see on the internet seems to be for power management. to support it you will need a hot air soldering station.
 

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certainly a rather complicated job ... but since the drone is not working, it is worth keeping to do some tests ...
to unsolder and re-solder you will need flux for smd.
 
Found the cause. It's a busted dual transistor(square, 6 legged). The engravings were "1C" and "W82" below it.

Only one of the 4 transistors heat up when battery is inserted. And if a transistor is damaged, it loses its ability as a switch and remain ON making the motor spin when battery is inserted

Unfortunately can't find a replacement of it anywhere on the internet.

My drone won't fly because that one motor with the busted transistor spins at a constant speed all the time. I'm wondering if it's possible to bypass the busted transistor with jumpers so the motor speed can still be controlled instead of constant speed so my drone can atleast fly.
 
Hello I sent you a greeting today I was repairing my tello drone I have it for a long time and I stopped using it because the engine had been damaged 4 today I found a company that sells engines with this design and I am very curious and versatile to repair this type of circuits I ordered 3 motors to have several replacements because I have had problems before, then connect the motor to the board with the respective polarity and when to test it insert the battery and the motor began to spin and heat up dangerously I cut to a finger trying to remove the battery, well what I want to get to is that I check and everything I had done was correct connect the polarities respectively as they should be check check and check and my only alternative was to reverse the polarities of that motor that you just finished change, and with that I solve my problem, I realized this by how the motor number 4 turns with the problem, it turned to the left when that motor should turn to the right.


I hope this information helps you because today I cut my finger and hopefully it will help you because it worked for me, maybe they are not manufacturing the motors with a respective polarity and for this reason you have the same fault that was presented to me.
 
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@Porriniz If you can read the English posts, why don't you answer in English?

Regarding your recommendation to "reverse polarity": What exactly do you want to reverse here? Just swapping the motor cables of a brushed DC motor will only reverse its spin direction. All the other posts in this forum - and especially in this thread - indicate clearly, that this is a problem of one of the motor controllers which may have been caused by overheating.
 
@Hacky Before continuing, I offer you an apology. I wrote in Spanish because I had activated the translator, sorry to the whole community. The first step is to connect the battery carefully and check in which direction the motor is turning and the propeller, take into account not to leave the battery in for a long time, it is only a quick check to see where the motor turns and it is removed immediately that it is having the problem because with this you can rule out the change of polarity the motors have a specific turn and if they have the reverse polarity this happens, it happened to me yesterday that I changed the motor of my phone and when I inserted the battery it started to turn like crazy alone the number 4 engine that I had just changed and I see that there are several people with the same problem. My solution: remove the solder from the cables that I had connected and the order I had was positive blue and negative black, so I put them negative blue and positive black and when I changed it I solved my problem because it stopped starting the engine when I inserted the battery .
 
In this image we can see the correct movement of the motors, the motors have to rotate in this sense.
PicsArt_12-17-09.34.35.jpg
 

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