Hey there,
having sometimes issues with Filament retract back into AMS Unit (just a little pull by hand fixes it),
does someone know if the AMS Hub has his own Motor for assisting the AMS feeding and retracting?
thinking about to upgrade the default feeder to the AMS Hub because of that, but if the hub is nearly the same as the feeder this would be a useless upgrade …
It does not. Its just a fancy $50 runout sensor/4 way splitter.
okay thanks for the info, i assumed the same
there is not a lot of photos/teardowns online to see,
but would be a very small motor if there is one 
It would be interesting to try and find better motors for the ams itself
I don’t think the motors are the weak point in the AMS.
yeah but if there where an additional in the hub it would help i guess
The hub/buffer also serves to add a bit of resiliency to the filament path, with the AMS pushing and the extruder pulling. A motor in the hub would make things worse.
When this has happened to me it was using CF filament and the issue was the tight curve right above the extruder. There are printable accessories that improve that PTFE bend that do help.
Get the Y splitter off of printables.com Ever since I printed one and put in replacing the connecter at the back of the printer (top exit) I havent had any issues retracting… Other than that, make sure all pfte tube runs are as straight as possible no bends etc… You would be surprised the pressure/tension a slight bend/curve can have.
i should add my AMS is a bit further away, because its on a pullout above the printer, because i dont want to waste all the space above in my cupboard and therefore the PTFE from AMS to printer is about 75cm long (this might be the issue) but for now its works again (just bend the PTFE between the buffer and printhead a bit differently)
Yes the AMS motors are weak. I pushed my chamber temp to 64 and the AMS motors cannot push passed the heat creep. But if you put the spool on the back of the printer, it can feed just fine.
I too would like to see about changing the motors in the AMS as they are quite weak. It seems you can’t put the AMS more than a foot or so away from the printer as well, or have excess bends in the ptfe.
Need to tear it apart to get the motor information.
My two units are on a shelf below the printer, with the tubing 3-4 feet. I rarely have issues. Consider printing and using one of these, which I find helps a lot. X1 / P1P PTFE Tube Guide to fix loading issues - best of both worlds by Adam L | Download free STL model | Printables.com
I did add something like this after that test, I’ll have to test again, thanks very much!
I’m NOT finding the AMS hub to offer any improvement on the filament retract - far from it. If anything it is adding drag to the filament path, and making the retraction issue worse. If the filament roll is mostly full or more than about 25% empty, its going to throw an error on retraction about two-thirds of the time; with a partly-full reel, it only fails about a third of the time 
So far I have tried weights in the spools, buttons in the AMS with some PTFE tube in them, and the toolhead PTFE pathway support. And the problem is as bad as ever. But there is a definite change of motor speed when the filament hits the AMS hub when loading, so that’s not helping.
I’d like to make the filament pathwway as smooth and straight as possible; does anyone know if I could use the PTFE tubing into slots 2 & 3 of the hub (instead of 1 and 2)? The two middle slots seem straighter than 1 & 4.