Re: Needle Assembly Shudders

Jim Stutsman
 

The needle shuddering is actually part of the power-on self-test. It moves the needle to the extreme left and right zigzag positions as part of the test.The fact that the needle assembly is shuddering would suggest that the zigzag motor is trying to move the needle, but not succeeding. Replacing the motor did not help, so either the gears that the stepper motor drives are bound up in some way (which your technician probably checked), or the transistor driving the stepper motor has failed. That would be on the A board, which is probably what they will suggest to fix it. This is a pretty rare problem, which is probably why they are trying to reach the head of technical services. Unfortunately they could have already ordered an A board and swapped it a couple of times in 5 weeks.

For the benefit of onlookers, any time the machine powers up to a "Raise presser foot and turn off" it means that one of the self-tests has failed. Usually this is because a sensor is just every so slightly out of adjustment, so the problem comes and goes, but if it is solid as in this case then service is the only option.

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