Last week, when I powered on my Philips CD Player (CD931), I heard some mechanical grinding noise and the tray moved only a few centimeters outward and then stopped.
The CDM9 tray loading operates like this. The tray has a linear row of teeth driven by a 10-teeth plastic pinion on a plastic pulley spindle which in turn is belt driven by a small DC servo motor.
All the teeth on the plastic pinion have been sheared. I searched the web and apparently numerous people have had the same incident happened to them. The small plastic spindle and pulley costs me nearly US$20 from a seller on eBay but I have no choice and ordered one.
Today, the new spindle arrived and I fitted it to the tray loading mechanism. I explicitly make sure that the end limit switches operates correctly before powering ON. The tray closing stop limit switch operates a few mms before the tray reaches mechanical stop.
With the tray fully extended outwards, upon powering ON, it retracts back into the player but the servo motor did not stop and made a struggling noise when the tray can move in no further. I cut power quickly and re-check limit switches but limit switch operation seems to be OK. I then placed a voltmeter across the motor and switches ON. The DC servo motor did not stop after end limit is actuated, but power to the motor is removed by the control circuit *after* the motor is struggling when the end stop is reached.
So, the designer is NOT using the limit to stop the motion but relies on the high motor stalling current to trip the travel.(eblc1388: Not true, see post below)
I understand why it was designed like that as it is quite common in places like factories or process plants to use torque as a means for stopping actuators. This make sure the actuators are really closed tight.
My complaints is why use flimsy plastic pinion gear that could not withstand repeated torquing operation? The said mechanical force is always on a specific spindle tooth because there is no slip between the pinion and the row of longitudinal teeth on the moving tray.
I don't want my new spindle to shear after just a while.
Any comments? Is there any recommendations or modifications for it?
The CDM9 tray loading operates like this. The tray has a linear row of teeth driven by a 10-teeth plastic pinion on a plastic pulley spindle which in turn is belt driven by a small DC servo motor.
All the teeth on the plastic pinion have been sheared. I searched the web and apparently numerous people have had the same incident happened to them. The small plastic spindle and pulley costs me nearly US$20 from a seller on eBay but I have no choice and ordered one.
Today, the new spindle arrived and I fitted it to the tray loading mechanism. I explicitly make sure that the end limit switches operates correctly before powering ON. The tray closing stop limit switch operates a few mms before the tray reaches mechanical stop.
With the tray fully extended outwards, upon powering ON, it retracts back into the player but the servo motor did not stop and made a struggling noise when the tray can move in no further. I cut power quickly and re-check limit switches but limit switch operation seems to be OK. I then placed a voltmeter across the motor and switches ON. The DC servo motor did not stop after end limit is actuated, but power to the motor is removed by the control circuit *after* the motor is struggling when the end stop is reached.
So, the designer is NOT using the limit to stop the motion but relies on the high motor stalling current to trip the travel.(eblc1388: Not true, see post below)
I understand why it was designed like that as it is quite common in places like factories or process plants to use torque as a means for stopping actuators. This make sure the actuators are really closed tight.
My complaints is why use flimsy plastic pinion gear that could not withstand repeated torquing operation? The said mechanical force is always on a specific spindle tooth because there is no slip between the pinion and the row of longitudinal teeth on the moving tray.
I don't want my new spindle to shear after just a while.
Any comments? Is there any recommendations or modifications for it?
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