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Problem w/Pitch Control: Dual CS 506

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dustingrant

New Member
Hi everyone,

So the pitch control knob on my Dual 506 doesn't seem to work. The stroboscope markings for both 45 and 35rpms aren't standing still (like they should be) and I tried adjusting this with the pitch control, but the pitch control has no effect on the markings. I just put a new belt on so I don't think that's the problem. Has anyone had this problem before? Does anyone know how to fix it?

Thanks.
 
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Which belt? The main drive belt, or the small, 4" diameter "toothed" belt that links the pitch control dial with the motor itself?
 
The main drive belt. I didn't consider the toothed belt. Is that the problem? Do I have to replace that or is there another solution?

Thanks.
 
Remove the platter and then turn the pitch control. You should see half of the belt turning the adjustable height motor pulley. If you see no movement, then the belt is most likely broken at the pitch control - where you can't see it.
 
Like Bill said, the toothed belt is one key suspect. There are also a few other parts that cause trouble. See the diagram from the manual (available from The Vinyl Engine if you don't have one). The speed adjusts when the belt turns a cam and variable thickness disc (parts 111 and 112) that cause a bracket (113) to press down on the spindle, (117) changing its diameter.. The spindle is supposed to restore its shape when the bracket moves back up. However, with time, it gums up and sticks. I have found that sometimes manually pressing down and releasing on the bracket and spindle a few times can free it up without chemicals. The biggest enemy of this mechanism is inactivity. That includes running the table but without exercising the speed adjustment knob.

If the belt is broken, you can still set the speed by trial and error without it. There is a small nut (110) that provides the gross adjustment to the mechanism. I have found it stable enough that when that is set, it will hold that speed for a long time. I once ran a 1246 without an adjustment belt for 2 years without any noticeable change in speed.

Fernando
 
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