how to

How to Replace a Hubsan X4 Quadcopter Motor

This article shows how to replace a motor on a HubSan X4 quadcopter. The items required for this job are:

  • A replacement Hubsan X4 motor, H107-AO3 (mine were purchased as a pack of 4 for £14.95 from RobotBirds).
  • Small Philips Screwdrivers
  • Tweezers or small pliers
  • Soldering Iron and solder
The tools required

The tools required.

These are the tools required for the repair. I’m actually using a 60W soldering iron, which I use for most jobs, but a smaller one will do.

My Hubsan is over two years old now, so it’s the original version without the LEDs on the motors. Also, as it’s getting rather old, the black plastic case is on its last legs and is missing a few bits of plastic here and there.

The top right motor is the faulty one which is going to be replaced.

The Hubsan X4 being operated on - the top right motor is faulty

The Hubsan X4 being operated on – the top right motor is faulty.

The first job is to turn it over and remove the outer case. This is done by removing the three Philips screws and popping the arms out of the motor pods. I find that it’s easier to remove the single screw at the top, pop out the top two arms and then remove the final two screws at the sides.

Bottom casing removed, note the damage to the plastic case.

Bottom casing removed, note the damage to the plastic case.

Next, carefully remove the two screws holding the PCB onto the top casing. While it is possible to make the repair with the PCB in place, I found it easier to remove it in order to access the wiring.Notice that I’ve put the screws back into their threads in the top casing in order to avoid losing them. The bottom case screws have also been inserted into the case, which I’ve put to one side.

The PCB is removed.

The PCB is removed.

The motor is removed by pulling it through the top, i.e. the propeller “upwards” direction. You can see from the picture that mine suffered damage by striking a wall from the top, driving the armature through the bottom of the weak plastic motor back plate.

Make sure to free the wiring from the motor to the PCB first so that the motor is free to move. In my case, the back plate and motor can were in two separate parts, and, with the propeller still firmly attached to the motor, it was an easy job to pull the motor out of its mounting. If this is not the case, use duct tape (or sellotape), stuck around the exposed top part of the motor can to pull it free. You could use pliers to do this if you don’t mind damaging the motor though. In my case, I had forgotten to take one of the earlier pictures, so I had to remove the good motor and put it back again later. The motor is just a friction fit, so the tape method works very well.

The defective motor is pulled out through the top

The defective motor is pulled out through the top.

Now comes the soldering part. Make sure the iron is fully up to temperature before attempting the soldering. On a PCB this small, temperature is critical. DO NOT allow the joint to heat up too much, or the PCB will be damaged. I’m using a 60W soldering iron, but I do have a lot of soldering experience. The hot iron allows me to get the heat into the joint very quickly to melt the solder, but I’m using less than a second of contact with the iron on the solder pad. Use a smaller iron if that’s what works best for you.

Anyway, introduce a LITTLE heat to the plus and minus solder pads where the black and red motor wires connect and allow the wires to come away from the PCB. The wiring can now be pulled through the motor mount hole and the defective motor removed completely.

Use as little heat as possible to de-solder the motor wires

Use as little heat as possible to de-solder the motor wires.

Motor wires removed.

Motor wires removed.

And the defective motor is removed.

And the defective motor is removed.

Now, locate the correct replacement motor. I found that, in my pack of four, there were two with red and blue leads and two with black and white leads. This matches the diagonals on the quadcopter (top left and bottom right, top right and bottom left looking from the top). My old motor was one with red and blue leads, so I selected an identical replacement from the pack of four. I can only assume that this is something to do with the direction of rotation, but I don’t know what the differences are. It is possible that the timing on the different motor directions is different, but I don’t actually know the reason for the difference, or whether a white/black motor can be used as a replacement for a red/blue one. They only cost a couple of pounds each, so its sensible to replace like with like.

The new motor is pushed through the mount into position, after which the wiring can be put into position.

Four motors.

Four motors.

Wiring goes in first.

Wiring goes in first.

Then push the motor through. Make sure of the orientation so that the wiring sits flat.

Then push the motor through. Make sure of the orientation so that the wiring sits flat.

When the motor is pushed into position, make a note of the rotation of the motor in relation to the wires. The blue and red wires need to be in line so that the wiring sits neat and flat in the motor pod. Look at how the wiring for the other motors has been accomplished and copy that. Here, it’s worth pointing out that the wires on my new motor are slightly thicker than the ones on the motor that it is replacing. While this is good in terms of quality, it also makes it a bit harder to push the wires into the slots that need to hold them securely in place.

In order to solder the wires in place, I fixed them in place at the motor end before attempting to solder. I also freshened the solder pads on the PCB and ends of the motor wires very carefully with some solder just to wet them and increase my chances of a good joint.

Don't use too much heat!

Don’t use too much heat!

Solder complete.

Solder complete.

Hold the wires in place while soldering any way that you’re comfortable with. Use fingers if you can do it without burning yourself (also prevents you using too much heat), or use tweezers of small pliers. My advice is to stick one wire to the pad any way you can, then do the other one. Now both have a mechanical joint, it’s easier to hold both in place together and add a little more heat if you want to remake a joint that you’re not happy about. Solder joints should be shiny and rounded, not dull and pitted, which is an indicator of a dry joint. You can give the wires a little pull if you want to check.

My soldering here isn’t actually all that good, but the key is good enough. Heat is the enemy, don’t melt the PCB and make the tracks come off.

The next thing to do is check whether this actually works. Put the propeller back on and connect up the LiPo.

It blinks, it beeps, it binds!

It blinks, it beeps, it binds!

Put the propeller on and see if it spins.

Put the propeller on and see if it spins.

OK, it seems to work, so put it back together and see if it flies.

Place the wiring back neatly in the guides.

Place the wiring back neatly in the guides.

Loop the motor wires underneath the PCB.

Loop the motor wires underneath the PCB.

Place the wiring back neatly into the guide slots in the motor pod, arm and joint into the main body. I used a small flat blade screwdriver for this, but something non-metallic would be better. Make sure to loop the motor wires underneath where the PCB sits, ensuring that they do not obstruct the PCB’s screw hole. When all the wiring is neat and tidy, screw the PCB back on.

Screw the PCB back on.

Screw the PCB back on.

And finally, put the bottom half of the case back, making sure to be careful when popping the arms back into their correct places. My case is so badly wrecked, it probably doesn’t matter any more.

The little Hubsan is as good as new.

The little Hubsan is as good as new.

That’s it, now go and fly the X4 to make sure it’s all good. You might have to do the “Expert mode, full right rudder, zero throttle, waggle ailerons left and right until the eyes blink” trick to reset the trim on a horizontal surface. Mine flew fine as it was though.

I would say it flies like a bird, but actually, think, “angry hornet with attitude…”.

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