What is resistor value inside tetrix motor?

We smoked a tetrix motor last weekend when testing a mini bot. An examination of the inside of the motor shows that there is a resistor, or something that looks like a resistor inside the rear cap of the motor.
It is this part that has no more magic smoke.
Try as I might, I haven’t been able to catch enough smoke to put back in there and so it won’t work. :ahh:
Does anyone know what this part is, and what it’s value should be?
I’m going to throw out a guess that it is a low value resistor, but since the color bands are burnt I can’t tell the value.
Thanks for your help with this.


Didn’t you get two motors? Any way, I’ll crack one of mine open and take a look if you tell us how you managed to “smoke” yours. And incidentally, how are you connected to the motor input tabs?

Putting the magic smoke back in is impossible!!!
Also, tetrix motors, with the stock gearboxes in place, HATE being geared up and put under a continuous load. (it’s OK for ball shooters and discontinuous high-load applications like that, but otherwise, the magic smoke escapes). Good luck.

You’re going about it all wrong.


Should be interchangeable, but it could be metric.

Magic smoke is like entropy, nothing you do can reverse the loss!

Post some pictures and maybe we can take a closer look?

Hi all,
Thanks for the thoughts on our smoke release. I do usually like to have spare smoke on hand, but in this case it seems to be special smoke that I don’t have.

Seriously, we had made a mini bot prototype which wasn’t much more than a sled with a ring of plastic to hold it on the to the pole. 2 kit wheels on 2 motors and the battery. It wouldn’t go up the pole very well as it didn’t have enough traction.

Some one wanted to measure the speed and so they set it on the floor where it ran for about 5 seconds and then a puff of the afore mentioned smoke came out of the motor and it started going in circles, i.e., the motor had died.

I’m a bit surprised that this happened, and I’m not sure that it wasn’t just a weak motor to begin with, but there’s no way to tell at this point.

Here’s a link to a pic of what we were trying.

I don’t have a pic of the burnt part yet, I’ll try to get one tonight.

Thanks everyone, have a great day, ::safety::


It could be a noise suppression capacitor, but replacing it may not solve the functional problem.Did you direct wire the motor, or fuse the circuit? :slight_smile: :slight_smile:

I believe it is an RF choke meant to suppress the incredible brush noise from the motor interfering with the electronics.
BTW, replacing it violates modifying the motors under R93, sorry.

Hi Al, all,
There is a separate cap in the motor as well, it looks like a small .1uF, that is fine.
I agree it probably is a choke, and yes, it won’t be legal, but for testing purposes it will work and since we only have the 2 motors at this time (1 good, and this one broken) we need to fix it just for prototyping.

Thanks again for your thoughts,