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Discussion Starter · #1 ·
Recently got a Powermatic PM2000 table saw. Today I installed the full set (all chippers & spacers) of a new Freud 208 stacked dado, in order to cut through a blade insert I had made for the dado. Slowly elevating the blade, the saw easily cut through the insert & the 3/4" pine board I had clamped across the table to hold the insert down. So far so good. Admiring my new insert, I decided to lower the blade to a height of about 1/4" and makes some practice cuts through some 2x4 scrap (this is my 1st experience with a dado). However when I pushed the on button, the saw would simply spin up for a second or 2, then shut down. Pushing the start button immediately produced no response at all. Only after sitting about a minute would the saw even attempt to power up, producing the same result; a brief, seemingly 1/2 speed spin up, then a shut down. It did this about 5 times. I opened the cover, the motor & all seemed fine, motor was quiet cool to the touch (it's about 55 in the shop). I pulled the dado (which took several minutes as the blades fit quite tightly on the arbor) and re-installed my WWII combo blade, and the saw started & ran fine. I have not yet tried the dado again (surprised what a PITA it is to install these, especially the full set) but I thought I'd post here in case anyone has any ideas about the events so far. In the manual troubleshooting section under "Motor starts slowly or fails to come up to speed", the causes listed are low voltage (line measures 237 volts, drops to about 232 for a ~half second on startup, then goes back to 237. Remains at 237 during a cut), bad motor & centrifugal switch, which I gather is located in the motor. Of these cause, the centrifugal switch seems the most likely. Maybe the additional mass of the dado slow startup slightly & the centrifugal switch cuts the power, perhaps because it's overly sensitive? Who knows. In any case it seems odd the dado ran fine at 1st. Again, if anyone has any ideas I'd like to hear them.

TIA

Dan
 

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Discussion Starter · #2 ·
I little more info on this. Tried running the dado with all blades, but minus the spacer pack. Saw runs fine. Added the shim pack, saw won't start. I can only conclude it must be that the added mass is preventing the blade from coming up to speed fast enough to satisfy the centrifugal switch that takes the motor from start to run mode. I opened the switch/contactor box & observed the goings-on. The saw attempts to start, runs slower than full speed, produces a sort of rattling sound inside the cabinet, and the overload trips on the switch assembly. Looks like a call to Powermatic is in order.

Dan
 

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Discussion Starter · #3 ·
I seem to have solved this one. Although I had checked this when the saw arrived, and although I have been using the saw for a couple weeks now as it was delivered, the apparent problem was a slightly loose belt. I observed the start up attempts with the side cover open, & noted some shuddering of the belt. Tightening it slightly (about 3/32" movement of the lower motor pivot point in the "tighter" direction) has seemed to eliminate the problem. Saw now starts fine w/the entire dado pack. Belts do stretch a bit on initial use, so maybe that's what happened here.

Hope this helps if anyone ever has a similar issue.

Dan
 

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If it was the wieght you shouldn't have gotten it to make the first cut. Are you sure the stack is free to spin in the slot when all the blades are on, have you tried to move it bu hand to check?
 

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Sounds like you've got things under control.

3 things that can cause identical symtoms are the start-up capacitor, thermal switch, and extention cords.

The cap phase shifts the input ACand gives the motor that little extra umph when trying to start, just to kick it over, so to speak. This reduces the amount of current the motor needs to draw through the wires to spin up. When the motor acheives the right amount of RPM, the cent. switch removes the cap from the circuit. Think of a garden hose for a sec. Bigger hose, more gallons/minute. Current works in the same manner. Small wires can't handle a lot of current, in some cases even the amount of current necessary to start the motor, under load, from a dead stop. This is why some motors, not all, use the capacitor. If it goes bad, you wind up like the guy in that video recently posted here.

A thermal switch, kind of like a circuit breaker, can be used also.
These are generally placed inside the motor case, either on the case directly or taped to the input wires. Its job is to disconnect the power source from the motor when temperatures get too high. Keeps the motor from having what we term a "Thermal incident". Current passing through a wire with resistance, and all wires have resistance, produces heat. The greater the current draw, the more heat is generated.
This is exactly why your motor wouldn't start for a minute or two. The thermal switch had to cool down. When a thermal goes bad, often they trip at a lower temperature than designed or they never close again.

And last, like I said earlier, all wires have resistance. As resistance builds, the transfer of power, read current, goes down. By using an extension cord, you increase the amount of resistance between the saw and the power source. This is even more so if you use an extension cord with a smaller guage wire than the saw. Basically you choke off the blood flow to the saw. This is a common mistake.

By adding the full dado pack and shims, you are demanding that the saw use more current to start than it would normally need. Look for the choke if the problem occurs again.
 
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