Mark V 500 Capacitor Failure?

[br549]

I just had to replace my switch (after 42 years), and it ran great for about an hour. Then it wouldn't start and only hummed, which I have come to recognize as likely caused by sawdust build up in the centrifugal start switch. So, took out 1 1/8 HP GE motor and opened it up, blew out dust and put motor back in. Still only hummed. Took motor out again and this time cleaned centrifugal switch contacts and re-bent arms slightly. This time it started, but it seemed to start (and stop) a little quicker than usual. Got re-set up to continue my sawing, and after a few seconds of running speed control up to "P" noticed light blue smoke coming from headstock. Immediately shut off. In the process of dropping motor fan, felt oily liquid on bottom of pan. Scrap of wood I had across bench tubes below motor pan (to support motor pan as I removed it) also wet with light oil. Capacitor compartment also has some oil inside it, and capacitor was very hot. Is this one of the rare instances where the capacitor has failed?

[garys]

Yes, that sounds like a capacitor failure. Nothing lasts forever.

[br549]

Thanks. Any suggestions on where to find replacement? Here are pictures of the old one. I tried searching by all of the numbers and no luck.

[garys]

Just take it to a local electric motor repair shop and most likely they have a new one on hand.

[JPG]

Relevant # are 161-193 MFD, 110v 60hz

You may have 'formed' the contacts too much so that the contacts are not opening and the capacitor was shifted from intermittant to continuous duty and subjected to excess voltage after startup.

[rogersk]

Thanks. Any suggestions on where to find replacement? Here are pictures of the old one. I tried searching by all of the numbers and no luck.

Attachments

This one at Grainger looks like it fits the bill.

Keith

[br549]

Thanks for the tips and suggestions. A local motor repair shop was investigated, but it would involve driving thru Houston, which I am becoming less inclined to do. I'll double check the centrifugal switch contact arms too, to be sure I didn't bend them too much. New capacitor that I ordered online is due to arrive tomorrow, so will post results after I get it installed.

[br549]

I temporarily changed the subject line, as my question now has to do with how the contact portion of the centrifugal switch works. After some confusion on my part, I think I understand it, but would appreciate a more expert opinion, confirmation, or correction.

On a GE motor such as mine, the round contact points need to be in contact in order to get the capacitor to send current to the start windings. Once the motor starts spinning, the spring loaded centrifugal mechanism drops down, breaking the connection at the round contact points.

The red wire from the capacitor is connected to the copper yoke, which is connected to the two aluminum arms. These aluminum arms are also energized when the copper yoke is energized, but the tips of these 2 aluminum arms do NOT need to be in contact with the copper yoke while the motor is starting.

Once the motor starts spinning, the spring loaded centrifugal mechanism drops down, and the copper yoke will (or may?) contact the 2 aluminum arms, but since the round contact points are no longer touching, no additional energy is being sent from the capacitor to the start windings.

There is also the second red wire from the capacitor that appears to connect to the start windings.

Is this summary correct?

[JPG]

The aluminum arms are a stop for the open position(running). This allows the yoke wear pads to clear the spinning sliding actuator thus only wearing when starting up. The sliding actuator should push the yoke and thus close the contacts at rest. The fly wheel weights cause the actuator to slide on the shaft. The actuator should be spring loaded towards closing the contacts.

I be guessing the arms are plated steel.

[br549]

Thanks jpg for the excellent verbal description of the function of all of the pieces. The purpose of the plated steel arms (you were right, not aluminum) now makes sense. My new capacitor arrived in the mail and all is back together and seems to running properly. Getting the copper yoke and the plated steel arms bent to the correct angles took a few tries, but finally succeeded.