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RE: no brushes
Posted by dick lucas on April 12th, 2004 12:58 PM
In reply to Sears (emerson) Radial Arm Saw by John on April 11th, 2004 09:56 AM [Go to top of thread]
Brushes are used on AC/DC universal motors such as are found in routers. They run at very high speeds, not at the constant speed required for a saw. Your motor is a capacitor start motor. Usually, the capacitor is in series with one set of windings which are used to give the motor decent starting torque. That set of windings is switched out as the motor comes to speed.
In my Sears RAS,( # 29410) the manual shows the capacitor located on a box on top of the motor. Your problem is likely caused either by that capacitor going bad, or by the switch being open. The usual switch is centrifugally operated, but I don't see it in the diagrams for my model. Instead, there is a relay inside that same box. I suspect that the relay is used to switch out the low speed windings.
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