Replies

1. 
   rob_ss | Dec 11, 2020 01:50am | #1

   **Not an electrician**

   Sparking generally indicates an intermittent contact. It would be worth cleaning the mechanism and making sure there is a good contact there, leastways, as long as it looks like there should be a contact. Intermittent contacts may also be unintentional contacts.
   The intermittent operation also suggests a poor contact.

2. 
   _mj_ | Dec 11, 2020 06:12am | #2

   3 phase power, old cast iron, and sparks sounds scarydangerous. Might be time for an electrician.

3. 
   Rob_Sp | Dec 11, 2020 08:56am | #3

   I'll second Rob's reply above...
   Both the hum (single phasing) and sparking indicate dirty or corroded contacts. Inspect and clean them, if corroded which is probably the case with an old machine, you can try to polish them with some fine sandpaper. You will damage the motor if you continue to run in this condition. It's not rocket science, just make sure you disconnect from power first.

4. 
   gulfstar | Dec 11, 2020 09:40am | #4

   If this is a magnetic switch and the part you circled is where the sparks came from it is the solenoid activated plunger that is malfunctioning. I had the same experience with my 1958 DeWalt radial arm saw and simply replaced the old box with a new one.

   
1. 
   user-7506761 | Dec 12, 2020 12:19pm | #5

   Thanks all!

   Gulfstar - do you have a part number for the unit?

   From my reading, it seems like the camps are split about cleaning contacts, but I’ll try that first with alcohol.

   Much appreciated!

2. 
   bbabbitt46 | Dec 12, 2020 02:00pm | #6

   That does look like a magnetic switch. Yes, the contacts could be corroded or burnt from "flashover." Alcohol probably won't clean the contacts. Having worked with many mag switches, I would take the switch apart to get to the contacts and burnish them with sandpaper. If you are not familiar with them, though, I wouldn't recommend doing that. In any event, contact cleaning is usually only a temporary fix. Your best bet would be to get a new mag switch. You can get them from Grainger or any electrical distributor. Pay attention to the voltage and amperage specs and, obviously, get a three-phase unit.

5. 
   gulfstar | Dec 12, 2020 03:36pm | #7

   https://www.amazon.ca/-/fr/18833-triphasé-220-240-volt-8-12-amp-commutateur-magnétique/dp/B002LVUWI6/ref=pd_sbs_60_7?ie=UTF8&language=en_CA&pd_rd_i=B002LVUWI6&pd_rd_r=1fe92557-e994-4468-ad7b-60363c0b21d0&pd_rd_w=DOIpx&pd_rd_wg=bbJd4&pf_rd_p=3885b243-7797-4c4b-b0ae-97ca9ec36283&pf_rd_r=1XSHJPVR77TF7CSSGMFR&psc=1&refRID=1XSHJPVR77TF7CSSGMFR

6. 
   user-7506761 | Dec 16, 2020 05:20pm | #8

   Thanks all!