Powermatic 3520B Noise interferrence problems.

[Larry Lilly]

Since getting the PM lathe, the home U-Verse and computer signal crap out when I fire the lathe on. I had heard about some noise issues regarding radio, but is this issue typical? During the weekend, at times as I was sanding a bowl my wife would come periodically saying the Uverse and computer signals died. I did some checking online and found some info, and then after thinking what she said, the next night I played with the lathe. I went out and fired the lathe up at a high speed (1200) Then I would wait for 10 seconds, and lower the speed by 200 rpm. I finally found after several speed lowering and speed ups that at LOWER than 200 rpm, the TV/Computer signal would die. I tried it several times. The TV would die, I would turn the lathe off, wait until the TV restarted (1 minute or so) then restart the lathe and speed it up before it died. After several times, it was evident that at least last night, at 200 RPM or lower, the TV/computer dies. At 225 and above, its ok.

Anyone else have this problem. Some had said to shield the lathe, but I do not know what that means. others have said line chokes. Is that just a pair of semicurcular magnets large enough to go over the power cord? One on the power cord, another on the cord from the electronic box back to the motor, both?

Any help would be greatly appreciated.

[Scott Conners]

Uverse TV has the option of using wireless receivers, and I'm guessing your computer is also using wifi. Both of these use 2.4GHz signals. The VFD from your lathe must be broadcasting interference in the band, or radiating RF noise in that band on the power lines. Using chokes (ferrite donuts or beads) on the power cord can help with interference being delivered through the powerlines. Also confirm that you have a good ground connection for the lathe. It needs to be properly grounded to the power receptacle (and box if the box is metal), and the receptacle needs to be properly grounded to the panel, which has to be properly grounded to earth. If it isn't properly earthed, the built in shielding of the components won't function as well.

[Larry Lilly]

The wiring was done by an electrical contractor earlier this month. The wires are in metal conduit attached to the sheetrock on the garage wall. The house main breaker box is less than 10 feet away from the dedicated lathe outlet, on the same wall. I had the electrician add a seperate switch on the right hand side of the lathe to kill the power to the lathe so I dont have to disconnect the power cord when I am not using the lathe for any extended time, and also it acts as a emergency kill switch so I dont have to reach across the spinning bowl if I have to shut the lathe off while its on.

The wall that this is on is the same wall that the Uverse cable comes in on. The Uverse cable gets split at the outside wall where the underground cable comes out enters the connection box on the outside wall, is switched to coax cable, goes up to the soffit, enters the attic and lays along the rafters to a point 60 feet away where it drops down to the Uverse router that is cabled into the Mac. A second line from the router feeds the TV.

After Christmas I will contact Uverse and tell them something is causing their signal to die. I can have the lathe running at low rpm and see what he says. To go outside, the tech will pass the lathe and probably say "there your problem" to which I will say, "and"

[Dan Hintz]

To be fair, the tech will rightfully point out the lathe (VFD) as the problem... FCC rules state nothing about the amount of interference the receivers can handle (or how gracefully they handle it), only the amount of interference equipment can broadcast (intentionally, or otherwise). I believe the VFD is a class A device (though I would verify that), and therefore has less stringent EMI concerns. If it's radiating a ton of noise onto the power lines, it's up to you to fix the issue (by removing the offending device from the line).

Any chance you could swap the boxes to the opposite phase? If so, see if the noise goes away... and if it does, the VFD is leaking too much noise into that other phase (which means it can be remedied). If there is no difference, you'll want to check the grounding... plenty of noise can end up there, especially if the ground of the lathe socket isn't solid.

That should give you a few hours worth of checking to do...