This is what the inside of a servo motor looks like

[Hedgie]

My servo motor (part 99498) recently broke and TLC kindly shipped me a new one. Instead of just throwing the old one away, I thought it would be nice to show you all some pictures of what the inside looks like:

As you can see, it took quite some aggression to open this thing. The dark gray part is fixed to the light gray part by only 4 plastic clamps, but they are so tight it's impossible to open it without damaging it. The plastic is also very soft, it's possible to scratch it even with just nails.

Here's an overview of the main components: 1) housing, 2) motor and circuit board (bent 90 degrees), 3) gearing, and 4) more housing.

Now it becomes clear why the circuit board is bent 90 degrees and how the system actually works. As the output shaft rotates, the two metal pieces slide over the contacts of the circuit board. Thereby the microcontroller knows what the current rotation of the output shaft is, and can stop the motor when it's reached the proper destination.

The motor itself turns much faster than the output thanks to this planetary gearing system. Unfortunately, I don't know enough math to calculate the actual gear ratio.

Obviously, this particular servo motor will never function again. It's a shame, because I've hardly ever used it and there is nothing that looks out of the ordinary. I suspect the problem was somewhere inside the wire, as I could sometimes make it function by wiggling it. Unless anyone here wants this motor for research purposes, I'm throwing it away

[Milan]

Why don't you take it to some electrician?

If it is wire problem, he can repair it.

[vmln8r]

I think wires are the weak spot for PF; I've had loads of L motors and a few M motors become unreliable in a similar way.

[aol000xw]

It is a shame that TLG made the wires part of the motors and to add insult to injury instead of a couple screws they use those terrible latches that prevent a safe servicing.

[zux]

It is a shame that TLG made the wires part of the motors

External wire would make motor-wire assembly at least 1 stud longer, wider or higher.

[skppo]

Yeah I think around 5 of my 8 m-motors are broken. Most likely the wire. And it's not like I handle them roughly >:(

External cord wouldn't neccesarily add any bulk if it wasn't stud based like the old system. The connector could be made really thin.

Then again it would cost more. I'd pay for that though.

[DrJB]

At issue is the WIDE ribbon like cable. SUch cables do not take bending too well. Would have been easier to make a round cable ... but cost would have been higher as well. Those wide/flat cables make it very easy to assemble and produce those motors in mass quantities ...

[Zerobricks]

Is the electric motor same as in M motor?

[Hedgie]

Is the electric motor same as in M motor?

They do look very much alike:

[Doc_Brown]

Very interesting! Looks like you used a bit of force to open it. XD

[gregorijs3kivi]

Why don't you take it to some electrician?

If it is wire problem, he can repair it.

yes, i do it