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CanoScan 5000F ..... stepper motor


I have a CanoScan 5000 scanner, which falters when initializing ... and also when scanning an image. That is, the movement of the scanning platform is not smooth, but 'stutters', and does not produce a successful image.
My initial guess is that the problem is with the stepper motor which moves the scanning platform. Another possibility is that the nylon gears that mesh with the output shaft of the motor have worn and are slipping. It is difficult to pinpoint the exact cause, since I have not been able to activate the stepper motor drive by itself ..... only when assembled ... and the case is closed.

Stepper Motor:
Type 14PM - M201 -G11ST
Minebea Co. Ltd.

My question at this time is whether this type of stepper motor can wear out?
I have disassembled this motor, and there is a ferrite stator ring, with fine, inboard, indentations, along with 8 radial coils. The rotor has a matching ferrite disk, placed in direct proximity to the stator.

There is no obvious sign of wear within the motor .... iron dust .... or anything else.

Is it possible that the gap between the stator and rotor ferrites has somehow enlarged or increased, thereby decreasing the motor torque?

.... Something that I am missing here?

Thanks ....


If the scanning unit moves along a metal shaft, check that it's suitably lubricated.
Friction doesn't seem to be the main issue. There is one rail that has a nylon glider. The other rail is chrome plated ....

Upon reflection, the scan platform only falters on the 'outbound', or scan direction, when it is trying to scan the image. When the platform is returning from the far end, back to the 'home' position, it seems to work properly, with a smooth action. This would seem to indicate that the stepper motor itself is not the problem.

Consequently, the problem might be with the 15" long black plastic toothed traction ribbon ..... something like a rack in a rack and pinion .... only consisting of a one sided toothed ribbon, which meshes with the drive gears on the scan platform. .... That is, the teeth on the ribbon may be worn on one side, and still intact on the other.

Would the worn traction ribbon be a possible cause?

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