Table saw won't start. Blade jump starts for 1/2 sec, but won't spin up.

[dirk martin]

I was about to rip 20 walnut boards, so I could then resaw them.
I jointed one edge on my jointer, then went over to my table saw to rip.

When I hit the power button, the blade gives a jump, but immediatly shuts off. Doesn't even give a full revolution.
I hit the red kill button, and it jumps again. Then the green button, and it jumps again.

It's clearly not a wall breaker issue, or the motor wouldn't even jump.
Suggestions?

Jet 5hp. Single phase.
It's clean under the table where the motor mounts.
All 3 belts are good.
Blade turns freely by hand.

[Erik Loza]

Short within the switch wiring, where the e-stop is being inadvertantly actuated?

Erik

[Ken Fitzgerald]

Dirk,

The most likely cause is a bad start capacitor on the motor or a lot of saw dust in the motor preventing the centrifugal switch from closing and inserting the start capacitor into the circuit.

First, I'd remove power and remove the motor. I'd pull an end cap and blowout the centrifugal switch. They look like the points in the old auto ignition circuits.

If that is okay, I'd remove the start capacitor. Sometimes they will swell or leak and can be troubleshot visually. Often they need to be checked with an Ohm meter or a capacitor checker.

These would be my first things to eliminate the cause.

[Peter Quinn]

We had exactly the same symptoms on a unisaw this spring, turned out to be a bad magnetic starter. The heater was kicking way too low and for no reason. Replaced the switch, everything back to normal.

[Mike Schuch]

Dirk,

The most likely cause is a bad start capacitor on the motor or a lot of saw dust in the motor preventing the centrifugal switch from closing and inserting the start capacitor into the circuit.

First, I'd remove power and remove the motor. I'd pull an end cap and blowout the centrifugal switch. They look like the points in the old auto ignition circuits.

If that is okay, I'd remove the start capacitor. Sometimes they will swell or leak and can be troubleshot visually. Often they need to be checked with an Ohm meter or a capacitor checker.

These would be my first things to eliminate the cause.

I blow out the case of the open frame motor on my Powermatic 65 cabinet saw every few years when it does this to me. After a good blow out (a little cursory blow out doesn't do the job) the saw is good again for another few years. I should just blow out the motor periodically as a preventative measure... and always say I will when it stops on me... but I never seem to do it until the saw forces me to. My problem has always been sawdust jamming the centrifugal switch.

First time this happened to me I removed the motor. Now I can blow it out quite well without pulling the motor off of the saw.

[Charles Lent]

Check the Stop button. Under normal conditions the switch behind the button is closed. It opens when you push the button. If it did not close again the last time you pushed and then released it then your saw would only run while you held the start button in and as long as you held the button in.

You should check the motor and the control box for excessive dust/dirt too. If the problem was the start capacitor or the centrifugal switch inside the motor, the motor would hum, draw excessive current and trip the overload protection in the control box.

Charley

[Don Jarvie]

To check it it's the switch or motor bypass the switch by wiring the motor directly to the plug. If it runs fine then it's the switch, if not the motor.

[dirk martin]

I was about to drag my air compressor over there, to blow it out, and I decided to press the switches a couple more times.
Lo-and-behold, it took off.

Thanks for all the suggestions....I'm prepared now, for next time.

[John Sanford]

I was about to drag my air compressor over there, to blow it out, and I decided to press the switches a couple more times.
Lo-and-behold, it took off.

Thanks for all the suggestions....I'm prepared now, for next time.

You should probably take the time ASAP to blow it out, otherwise "the next time" may be a lot sooner than you hope.

[Peter Quinn]

Might be time to order a new starter. Ours started with an intermittent episode like yours, then back to normal, then problematic again, then dead. Over a several month period. Finally got fixed when we were down for most of a week, you don't miss a machine until it's gone.

[Myk Rian]

First, I'd remove power and remove the motor.
Ever try removing a 5hp motor? Not much fun.
Just blow the motor out, in place.