Troubleshooting Noisy Startup on a 12-Inch Jointer
Could be a failing magnetic switch. November 16, 2010
Question
I have a General 12" jointer model 780 with a Baldor 3 hp motor. The machine is a couple years old, and is run in a woodworking school, so it is really well maintained. It is a great machine, and it has always run great. But it has a funky startup problem sometimes. It has a magnetic switch - when you push it on, it fires right up and all is well. But every once in a while, it will make a horrible racket when you fire it up and you have to shut it down; if you start it up again, it will be fine. It seems to only do this if you push the switch fast. It's not the head or bearings. The motor is good. It's got good belts. Everything is tight. You could put a dime on edge and run the thing and it would not fall. And it runs quietly, no abnormal sounds. So I'm thinking it has something to do with the motor - maybe a bad connection. But I went through all the electrics and everything seems okay. Could it be the switch?
Forum Responses
(Solid Wood Machining Forum)
From contributor J:
Can you be more specific about what the "horrible racket" sounds like?
From contributor E:
Is the noise more like an electrical hum? If so maybe it's a bad switch.
From contributor A:
I've got an 880, the big brother to your machine. It also has a funky noise on startup. We've narrowed it down to a bearing in the motor most likely. We took the belts off, spun the head - those are fine. Start up the machine with no belts, still get the noise. There is a very slight tick turning the motor pulley by hand. It sounds fine once it gets going, so I don't have to shut down. Try to see if you can isolate it that way. You can call JD at General - he's pretty helpful.
Great machines, aren't they? I was edge jointing a huge 8/4 slab of jatoba yesterday, being very happy that I didn't have to do that on a smaller machine because it would have tipped over!
From the original questioner:
The noise sounds like something is vibrating really hard. I will pull the belts off tomorrow and check the motor out. It is such a beautiful machine. After having this baby, I don't know how we did it before. Such a solid machine. In our shop we run mostly General machines, and I am so glad we went that route. We have a couple older machines (Davis and Wells bandsaw and boring machines, and a beautiful Wadkin sliding table saw). The Wadkin is a couple hundred pounds more than the jointer. That is a solid machine. But that jointer does a beautiful job.
From contributor P:
Magnetic switch contacts are burnt. Plan on replacing it soon. It may even knock the motor out if one leg of power drops due to the switch.
From the original questioner:
Thank you - I will order one ASAP. That makes the most sense to me.
