Maplenoll platter stability question

I sent in a detailed response last nite, not sure what happened but in a nutshell, one significant possibility for your problem is a worn centering pin (teflon) on the bottom base plate of the air bearing. I had a similar problem that i corrected by replacing that pin. If the moderator does not release the my response, you can PM me and i will help you diagnose the table to see if that is the problem

Hello Oilmanmojo,
Thank you for your kind response. Am I correct that a proper, unworn, center pin allows no side-to-side movement when fitted to the opening of the top plate? Or, does the pin act as a centering point and the spinning lead platter completely floats with no contact between pin and top plate? I hope this is understandable.

Great question and hopefully i can answer correctly. The centering pin (teflon i believe is the material if i remember lloyd right), serves the purpose of ensuring as the platter floats on the air between the plates (very small clearances) that it stays centered and does not move side to side as the platter turns. Remember the belt will put a slight force on the platter so sufficient friction exists to spin the platter. This means the platter pulls slightly towards the pulley attached to the motor. Now if the pin is slightly worn, but the platter is perfectly level and balanced, no major problem because the force is parallel to the platter and does not cause wobble. But if the platter is not perfectly balanced, then as the heavy side spins, the clearance will be lower on that side versus the light side. Again if the center pin is perfect, and the imbalance is low, then you do not see much if any deflection because the imbalance is just offset by a little friction on the pin. Since teflon has very low frictional properties, you do not see much impact. in fact you will be able to determine this if you carefully reduce the platter air pressure just to the platter just rubs. I found that if you listen carefully the imbalance will be an rhythmic sound and not continuous. if the platter is perfectly balanced the sound will be continuous. I know this sounds a little black magic but it works. If the platter is off balance you compensate by adding more air pressure which lifts the platter a little higher thus offsetting the imbalance Again you will see this by looking at the top of the spindle. It wobbles.

Now there is one other possibility and that is the spindle is bent slightly. If that is the case, the spindle will wobble but your tone arm will not move up and down. Look at it carefully. You also can get a carpenter square to determine if the spindle is bent.

hope this helps

tomg

I believe I can have a friend make a replacement center pin for me. I also think I can find a Teflon rod at US Plastics. I've recently replaced the belt and the increased pulling has caused the side-to-side movement to be more apparent. I have noticed the periodic rubbing when the air pressure is reduced. I don't have a source to balance the platter, unfortunately. I have read the owner's manual and have "trued" the top plate's spindle by lightly tapping on it. I finally have a good source of high enough air pressure. So the centering pin is the last hurdle.
Thank you, very much, for the information.

If you have a good machine shop where u live they may do it for u. Good luck and let me know how it comes out