DW788 Rebuild

[Rick_B]

Well I stepped away from this saw again. Once it got cold outside I had no more excuses

. This saw has two problems - noise and a motor speed control that seems to cause the speed to surge and/or slow down a bit as the speed control is increased. I've decided to focus on the noise issue - assuming the speed problem is unrelated to noise. Following are the steps I have followed so far:

1. Secured to saw to the benchtop - a VERY slight improvement to noise level but not enough to even consider victory. Noise presented as slight at lower speed setting of 1, increases with a knocking sound at 2 and 3, knocking reduced but still noisy at 4, knocking worse at 5 and knocking much less but still noisy at 6 through 8.

2. Applied a layout bluing to top and bottom of tension rod cover and retested. No indication of damage to the bluing which would indicate that something was contacting the cover.

3. Checked all upper and lower arm and chuck connection fasteners and retested - no change to noise levels

4. Adjusted tension rod one full turn CW - Noise/knocking seemed better but still unacceptable

5. Adjusted tension rod a second full turn CW - knocking significantly worse at speed 2 and above

6. Adjusted tension rod a third full turn CW - significant knocking at higher speeds - 5 and above

7. Adjusted tension rod 4 full turns CCW (3 back to starti g point +1) - Serious knocking goes away but still very noisy at various speed

8. Adjust tension rod 1 full turn CW - back to initial start point

So now I'm lost - can't really tell where the noise is coming from even with a stethoscope. The next step is to remove the left side covers and test the machine to see if that helps identify the noise source. I don't have a lot of hope for success but/I am open to any suggestions.

In addition to the noise I believe there is something wacky with the speed control causing the surge/speed variation but that's a problem for another day.

And oh yeah - I stripped a threaded hole in the upper rocker mounting casting 0 least of the issues at this point.

Rick

 

[Charles Lent]

For your speed control problem, a new speed control potentiometer may help. They are only a few bucks, but you will need to find an electronics supply house to buy one. Radio Shack is gone. The shaft may be way too long, requiring a little work with a hack saw, and it won't have wires or a connector, so you will need to transfer those from the old potentiometer. You should be able to buy one for less than $5 plus shipping. Make certain that you buy the same type as there are many versions of electrical as well as mechanical differences. DeWalt wants to include one with a new control board, and the last time that one was needed you couldn't buy one without buying the whole board, even though it just plugs into the board wiring.

Noise sources are hard to find, but the usual location is back at the motor, connecting rod, and rocker arm, and the bearings and pivot points there. Have you checked the condition and tightness of the bolt at the pivot point of the vertical rocking arm center? This bolt broke one time on mine, and loosened itself up several times too. Good bearings with no play at in their races in the connecting and rocker arms are important too. Is there any play in the motor shaft bearings? This is a wear point frequently never checked by those looking for noise in these saws.

Charley

 

[Rick_B]

Thanks Charlie - I appreciate your thoughts. I was headed down the path of replacing the potentiometer - if for no other reason than to eliminate it as a source of problems. I hope to get it disassembled today and try to identify its specs.

Then I want to pull off the left side covers and see if I can better pinpoint the noise source

Rick

 

[Rick_B]

Unfortunately I have been side tracked by a bedroom update and haven't had a chance to try anything with this machine for awhile. I will be getting back to it soon I hope and will post an update.

Rick