Grrrr ^&*#@&

[Al W]

There I was, happily cutting along and time to change the blade, still know how to do that.....

Repositioned the project, tightened up the blade, and stepped on the foot switch, then I stepped on the foot switch again, and again, .........nuttin'.

Electrical power is present at the wall, the foot switch works (tried it with a radio), and I checked the continuity of the switch on the saw, the switch works.  DeWalt saw, type 2. 

Finally got the saw to run when the neighbor came over and we spun the motor with a screwdriver - ran fine - until I turned it off again.  Won't start again. 

Checked the brushes and they appear fine.  The motor rotates easily with a screwdriver, and will take off if the power is on when I use the screwdriver to rotate the motor.

Your thoughts??

[scrollgirl]

The switches are a known issue with DW788 saws.  The good news is that they are only about $15, but the bad news is you will probably need to order it.  The switch just seems to give out at no reason.

Good luck, Sheila

[Al W]

Sheila,

I took the switch off of the machine and performed an ohms (continuity) check - switch works as it supposed to work.

Next Idea?

[Al W]

Okay.  Got the saw started again, by turning the motor, now I have NO adjustable speed, and yet the rheostat checks out fine with the ohm meter.  The motor is spinning VERY slowly, almost like it is set on 2 or 3 for the speed. 

Sigh.  This is not looking good.

[rob roy]

Hi AL, suggest you get the motor windings checked. Could be a short in one of the windings. Hope this helps Al.
Rob Roy.

[rob roy]

Hi Al, should have mentioned. Also check the starting capacitor. A small canister type thing bolted to the motor somewhere. This is used to give the motor a boost to start it, much like what you are doing with the screwdriver. Hope this helps.
Rob Roy.

[chippygeoff]

I had a similar problem and it proved to be the brushes that needed replacing on my 788.

[alien11]

Remove and check the brushes and the brush pockets for damage and sawdust. If the brushes are damaged or worn replace them. I'm guessing sawdust is your problem.

Since there are brushes on this motor that makes it a "universal" motor and there is no starting capacitor.

[Al W]

Short update. I removed the motor from the saw assembly and cleaned the armature contact area with emery cloth.  I also removed the brushes and lightly sanded them to remove any burnishing. The bearings are beautifully free moving. I then used compressed air to blow out the motor housing and did get some dust, albeit not sawdust, out of there.  There is NO start capacitor for the motor.

Put the whole shooting match back together, turned on the saw, and...................same ole problem.  

Spun the motor with a screwdriver to get it going, and now even with the speed control rheostat set at the highest speed, I get variable speed from barely moving to almost what it should be running.

Any chance the rheostat could be the trouble?


Al

[alien11]

Al:

That's a bummer. It sounds like you did a great job cleaning the brushes and the commutator.
The fact that you have no control over the speed suggests that the motor-control board has a problem and the rheostat is a component of that board although its not mounted directly on it. The board is located at the back of the saw opposite the motor. You've already checked the rheo so that leaves the board and the connections between parts. I hesitate to tell you to replace the board because it's fairly expensive. Try unplugging and replugging all connections that you can. Check all the wires from the input to the motor for damage. If that doesn't work out then the fault must lie either in the control board or the motor itself.

Hoping for the best for you.

[rob roy]

Sorry Al,I wrongly assumed it was an induction motor.
Rob Roy.