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Mk5 motor troubleshooting/Viejo

#249226 by Viejo » Sun Jun 10, 2018 10:52 pm

JPG- you're right, the motor did not jerk but simply stopped after a very brief attempt at rotation and then continued to hum until I opened the switch (~1.5 seconds).

Cheers,

Dave

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Viejo- Mk5 Greenie, s/n 328507 (second owner), shaper, 4" jointer, 18" jigsaw

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Re: Mk5 motor troubleshooting/Viejo

#249228 by JPG » Sun Jun 10, 2018 11:25 pm

1.5 seconds is good news! Not long enough to cause damage.

The motor 'start' circuit consists of three things.
1) the start windings.
2) the start capacitor
3) the start switch.

Those three things are connected in series(daisy chained)

The motor 'run' windings are directly connected to the external wires.

It is the 'run' windings that create the hum.

When power is applied to the external wires, both the run windings and the series start circuit are energized.

The most likely culprit to fail in the start circuit is the start switch.

At rest the switch contacts are closed and complete the series circuit so current flows to the start windings through the capacitor. This causes the armature to start to rotate(ain't really all that simple, but for current purposes it will suffice).

As the armature increases rpms a centrifugal mechanism opens the start switch contacts and the start circuit becomes non energized.

When it is turned off, the centrifugal mechanism closes the start switch and the cycle is set to repeat.

So we need to take a close look at the start switch. It is inside the motor(unless it is a GE motor with an external start relay).

Nuf fer now!

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╔═══╗
╟JPG ╢
╚═══╝

Goldie(Bought New SN 377425)/4" jointer/6" beltsander/12" planer/stripsander/bandsaw/powerstation /Scroll saw/Jig saw /Craftsman 10" ras/Craftsman 6" thicknessplaner/ Dayton10"tablesaw(restoredfromneighborstrashpile)/ Mark VII restoration in 'progress'/ 10E(SN E3779) restoration in progress, a 510 on the back burner and a growing pile of items to be eventually returned to useful life. - aka Red Grange

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Re: Mk5 motor troubleshooting/Viejo

#249233 by Viejo » Mon Jun 11, 2018 10:28 am

JPG wrote:1.5 seconds is good news! Not long enough to cause damage.

The motor 'start' circuit consists of three things.
1) the start windings.
2) the start capacitor
3) the start switch.

Those three things are connected in series(daisy chained)

The motor 'run' windings are directly connected to the external wires.

It is the 'run' windings that create the hum.

When power is applied to the external wires, both the run windings and the series start circuit are energized.



The most likely culprit to fail in the start circuit is the start switch.

At rest the switch contacts are closed and complete the series circuit so current flows to the start windings through the capacitor. This causes the armature to start to rotate(ain't really all that simple, but for current purposes it will suffice).

As the armature increases rpms a centrifugal mechanism opens the start switch contacts and the start circuit becomes non energized.

When it is turned off, the centrifugal mechanism closes the start switch and the cycle is set to repeat.

So we need to take a close look at the start switch. It is inside the motor(unless it is a GE motor with an external start relay).

Nuf fer now!


JPG- got it, thanks!... will update when the dust settles.

---

Viejo- Mk5 Greenie, s/n 328507 (second owner), shaper, 4" jointer, 18" jigsaw

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