[SOLVED] Shorted the M3 Motor

[jlevDev]

Hey everyone,

I had to solder the M3 wires back together which left them open and they accidently touched while I was flying. Now the motor spins at full speed when the battery is plugged in and none of the others are responsive. I guess I shorted it. Anybody have an idea what happened and if there is a way to fix it?

Thanks,

Jason

[tobias]

Yes, you can most likely fix it. Do you have a multimeter? My guess is that the M3 mosfet transistor shorted and needs to be replaced. This can be verified by measuring the resistance between the two yellow circles in the picture. If there is a short (~0 ohm) you need to replace the PMV31XN transistor marked with blue in the picture.

[jlevDev]

Hi Tobias. Thanks. I thought it was doomed. I do have a multimeter and I'll check it this evening after work. If I get it working again, my next project is to get those training wheels installed

[tobias]

I'm pretty sure you will be able to fix it and we are here to help you out . Keep us posted!

[jlevDev]

I tested the resistance last night and it is reading differently than the others. All the others had a resistance of about 5.5 on the lowest setting of the multimeter, and M3 was reading 0.7. I'll do my best to replace the transistor. I'm guessing the best way to do that is by using a solder sucker to remove the transistor?

[tobias]

When I have been changing transistors I have just used a tweezer and soldering iron.
I start by heating up the single leg and pull that side up with the tweezer. The other two legs will bend a bit but that doesn't really matter. I then do the same with one of the other legs and finally the last one. Don't pull to hard though as you risk getting the solder pad with it in the process. That is pretty hard to do with a tweezer though. After that you can remove the solder on the pads with a solder wick to make it easier to solder back the new transistor. I'm a bit laze though and just reuse the solder and heat it up leg by leg until it is soldered again. Some flux will help at this stage to get a nice soldering.

[jlevDev]

Tobias,

Thanks for your help. Replacing that transistor worked great. I made sure and put some heat shrink around those open wires this time. That was not easy. I used 15W on the soldering iron at first, but it wasn't melting the existing solder so I bumped it up to 30W and it worked. Those transistors are very tiny. You must have a better magnifier that I do. I could barely see if I was getting a good solder. Now to work on the training wheels. I think I read some where that the training wheels hack uses steel wire?

[tobias]

Great that you managed to fix it! Soon you will be easily changing QFN packages

Some short information about the training wheels here. You can also try some 3D printable parts.