Jet table saw smoke and sweet smell
Hello everyone I have an old Jet Jtas-10 table saw running on 220 that has been working great for me until tonight a smell was coming from it then a little bit of smoke so I turned it off. I felt the motor and one of the bumps (for the lack of a better term) was extremely hot. Not sure if it’s related but I had just changed the blade for the first time since buying it several years ago. I had been running it solid for probably over an hour. It was a very unique smell very sweet and I did notice a few black shreds of something inside the machine on the sawdust. Seems like the belts have a lot of slack in them how much slack is suppose to be on them?
Thanks in advance for the help I’ve got lots of work to get done so this is happening at the worst time.
Update: I let the saw cool down for a couple hours and just started it up and immediately shut it down and that small bump is immediately really hot. Is that the capacitor?
Replies
those bumps, and you probably have 2, are capacitors - one startup, and one run. if hot and smokey time to replace - the capacitance will be written on the side and easy to replace.
Only one of the covers/bumps were hot does that mean only one is bad? Do I need to discharge them before removing?
You will need to discharge the capacitor by taking a screwdriver and shorting the terminals. Unplug the machine before doing so. I personally would change both, they aren't expensive just to be on the safe side.
As for the belt I would replace it. Sounds like it has stretched and is shredding itself.
mcginnis is quite right . Those bumps are capacitors,one to get the motor running and one to keep it running. Commonly known as start and run capacitors. If you don't want to spring for a new motor, I would definetly replace BOTH capacitors, you don't know whether the other one is on it's last legs or not. It may be hard to find a new capacitor to fit in the shroud, manufacturers are always changing the shape and design. As far as belt tightness is concerned, it's hard to explain in print. I would say snug but not taut.
A drive belt should have about a half inch of deflection. Too tight and you will destroy the bearings and too loose you will burn up the belt through slippage.
Going down the road of ruling things out, I would remove the belt and then rotate the blade by hand. If it doesn't rotate freely, one or both of the trunion race bearings have failed and will need replacement (along with the belt and capacitor).
That's the first time I've heard capacitor stink described as 'sweet' but I suppose it is a bit now you mention it.
The Capacitors consist of a couple of sheets of foil with an insulator between them and usually some form of liquid dielectric to improve the capacitance. over time, they dry out and can burn internally, creating a small short. This causes heat which dries the capacitor more quickly and in no time at all they are useless. Probably using the motor for such a long time burned out an old capacitor - it is important to note that light duty machines are not intended for prolonged use and are more prone to fail if their design duty cycle is exceeded.
Replacement is the only option - do buy a decent quality alternative if you can from Mouser or Digikey or another trusted supplier rather than online auction/sales sites, as parts there are commonly not quite the specification on the can.
If you can't get an exact match then buy a higher voltage spec rather than lower. Higher voltage parts are higher quality and last longer. Capacitors are commonly +/- 25-30% on the capacitance so there is a lot of wiggle room in the number of uF, but closer to the original spec is always best.
Slipping belts generally cause a burning rubber smell - if your blade is stopping but the motor is still running then they need to be changed, but otherwise I'd not worry about it - like as not they are as intended.
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