Motor making an unwinding noise ?

Today when i was shooting my CTW i noticed that after it shot it would make a unwinding sound weather i shot on semi or full auto, so i broke down the gun and pull the trigger the the upper receiver off just to check the gears and there is hardly and active brake at all, on semi when i full the trigger the gear stops so far forward that it almost completed two cycles. what could cause this ? I was thinking the mosfet or motor.

Inside the buffer tube, there is an electronic circuit with 2 mosfets on it. One is responsible with starting the motor and the other with active braking it. Most likely, the "other" mosfet burned. This often comes with a strong smell of burned plastic - if this is your case, then you have 2 replace it.

You need someone that knows to solder a mosfet and also you have 2 extract the circuit board from the buffer tube - one way will be to: remove the battery, take the motor grip out, unsolder the 2 power wires from the motor, take the buffer_tube's cap, pull the power wires from the motor, carefully take out the mosfet board from the buffer tube, then remove the command wire plug (the 4 thin wires) from the it and that's it.
Be VERY careful with the command wires, as they are extremely sensitive..

I checked the mosfet it seemed fine, motor seems fine, eyes are clean on both sector gear and ecu, I really dont understand what the problem could be. I just made another video because its easier to do that then try to explain everything.

https://www.youtube.com/watch?v=uAOyBr_llbk

Its a new on me - the only thing that you've not looked at is the control cable from the trigger to the ECU.

I had to repair a mates CTW that was doing something similar, and I tried all the usual stuff, found nothing, then replaced the trigger control cable (its only about £7) and all sorted.

If thats not the cause, then the only thing left would be the motor brushes as they do wear, and this is what stops the motor - hence if there worn they wont stop the motor as quickly.

Well i took the gearbox out to check the control wire it also looks fine. no cuts no splices, nothing, However after i got the gearbox out i noticed something else(look at the pic below)



Its two shims super glued into place... Maybe this is what caused the screeching noise i spoke of in my earlier post ?

Dude, come on, revealing the celcius secret uber_technology

I discovered the same... don't really know how to call this.. thing when I took my gearbox out; it seems that the shims adjust the height needed for the sector gear to reach the piston teeth.

I think we can call this the shim_mod

I was curious to find out what exactly they did so i took them out and after re assembling the gun i noticed that the selector switch was very tight without them, even if the allen screw was barely in.

have u disassembled your gearbox recently? maybe you installed the sector gear backwards

No i haven't taken that apart, and i checked the brushes there fine. I saw that someone else had a problem similar to this and he got a new mosfet and solved the problem so when i get paid im gonna buy the FCC micro mosfet.

The shims are there to ensure the gear box is level with the top of the receiver.

They are not present in all CTW's, but they test them all at the factory when they are made, and if the gearbox is sitting a little low they put in the shims to make sure there is agood positive contact with the piston.

FYI the original Systema's that were introduced approx 4 years ago also did the same - some had shims, some did not.

this happend to me recently and after a few round my motor gave out. hope its not the case with yours.