Marantz 6350Q platter spins back and forth

[jmterlep]

I just picked up a Marantz 6350Q. New to the vintage turntable scene. Why does the center spindle spin back and forth if the platter is not on and when you put platter on, it spins? I'm sure this is turntable 101 but was curious how it works.


Thanks,
Mark

[ATHERMOS]

That is the way it is supposed to be, perfectly alright. Without the platter the rotor speeds up and overshoots the set speed, the Frequency Generator (FG)sends a feedback to the control circuit which cuts off power to the stator windings , causing the motor to slow down(turns only by inertia now).Again this is sensed by the FG which sends a signal to the control circuit to energise the motor and the thing repeats.

[jmterlep]

Thank you for the explaination! The other day when I turned it on, the platter was going back and forth also in stead of spinning. That is why I took it off and noticed the center spindle doing the same. Platter has spun fine since. Any ideas why that would have happened?

[ATHERMOS]

Such a thing usually happens when the Hall sensors (or even optical sensors ) are unable to determine the position of the rotor ,this could be a temporary phenomenon due to some obstruction on the way . If it assumes a permanent nature then the position sensors may be checked for their correct operation.

[jmterlep]

OK. It has assumed a permanent nature of spinning back and forth. What are the position sensors? Would that be the Hall sensors? Don't see any optical sensors.
Not sure where to start looking at to fix issue. FG, hall sensors, or something else?

Thanks,
Mark

[ATHERMOS]

1. Please check and clean motor including HAL effect sensors ( for ferromagnetic magnetic dust) if present under the rotor.Then please power on to see if that has solved the problem.

2.If the motor still does not operate then it is more complicated.

3.6350Q seems to be the quartz locked version of 6350 , the service manual of 6350 does not show the details of the DD motor. Hence I would request you to post pictures of the motor interior after taking it apart carefully.