# Two speed motor question



## yellow_cad (Jun 20, 2012)

I've got an 8X18 Jet lathe with mill head made in the 1980s.  The lathe uses a single phase 110 volt two speed motor that uses a capacitor to help it start under load.  The electrical switch is mechanical and obviously has a forward button and a reverse button.  It also has a button (longer than the f/r buttons so pushing more mechanical levers down) when pushed with either the forward or reverse button that drastically changes the geared speed (sort of like half).  Here is my issue: when only pushing, say, the forward button, I get the series of geared speeds that are listed as those coming from the low speed portion of the motor.  When I push the forward button along with the speed altering button, I go to about half of the lower range but pretty soon, I see smoke coming from, I believe, my motor.  Does this indicate that my two speed motor has lost its high speed range?  I don't want to get in a hurry to pull it out to have it rewound, if I'm just missing something.  Thanks for any input.  Jim


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## franklynb (Jun 21, 2012)

Is it possible that the capacitor is a RUN cap, not just starting cap? If so, and its failed/failing, that
would account for the motor inefficiency at high speed & load. Verifying a capacitor -- other than
an open failure -- sort of requires a special meter or oscilloscope, unless you're familiar with checking
circuits by building a simulator...

hth.

--frankb
Jim wrote:


yellow_cad said:


> I... I go to about half of the lower range but pretty soon, I see smoke coming from, I believe, my motor.  Does this indicate that my two speed motor has lost its high speed range


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## yellow_cad (Jun 21, 2012)

The first thing I had to do to this machine is to replace the milling head capacitor but the lathe capacitor looks to be the original one by the way it fits and how it is connected.  Could it be that even though it is there and hooked up, that it is not providing any capacitance?  Would the system run with a capacitor that is not functioning or minimally functioning?  Jim


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## SamIAm (Jun 23, 2012)

yellow_cad said:


> I've got an 8X18 Jet lathe with mill head made in the 1980s.  The lathe uses a single phase 110 volt two speed motor that uses a capacitor to help it start under load.  The electrical switch is mechanical and obviously has a forward button and a reverse button.  It also has a button (longer than the f/r buttons so pushing more mechanical levers down) when pushed with either the forward or reverse button that drastically changes the geared speed (sort of like half).  Here is my issue: when only pushing, say, the forward button, I get the series of geared speeds that are listed as those coming from the low speed portion of the motor.  When I push the forward button along with the speed altering button, I go to about half of the lower range but pretty soon, I see smoke coming from, I believe, my motor.  Does this indicate that my two speed motor has lost its high speed range?  I don't want to get in a hurry to pull it out to have it rewound, if I'm just missing something.  Thanks for any input.  Jim



Jim, 
Have you tried looking here?
http://www.jettools.com/us/manufacturing/en/service_support/manuals.html


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## Alan Douglas (Jun 23, 2012)

> Would the system run with a capacitor that is not functioning or minimally functioning?


Probably, with much lower torque.


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