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saw problem DW 788


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#1 ike

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Posted January 11, 2017 - 06:57 PM

My DW 788 stooped running. I was cutting 3/4 popular and doing fine then the saw stopped add then started back up  thought it might be dust so I blew out every thing it ran for about 1 minute stooped then started again the stooped again for the last time. I checked the switch , fuse, and brushes all were good. I am afraid that it is the motor or the mother board. any ideas out there.

IKE



#2 heppnerguy

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Posted January 11, 2017 - 08:18 PM

Have you tried taking some of the saw body apart and taken a physical look at the inside.. It is easy to do and I can give you a link as to how to do that, it you need it.

Might be a broken part inside or you might recheck everything external once more before going for the inside. Try moving the extended part where the blade connects, up and down by hand and see if it moves freely. Also double check the outlet and make sure it is hot and not tripped. If you have a meter you can take off the switch control, Only 4 torx screws and see if you are actually getting power there or if a wire has come loose of broke..

 

 

Dick

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#3 NC Scroller

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Posted January 11, 2017 - 08:48 PM

Un plug the saw then look at the end of the motor.  In the center you will see small slot like a screw.Using a screw driver turn it about a 1/2 turn (either way).  Then plug the saw back in and try again. 


Scott


#4 LarryEA

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Posted January 11, 2017 - 11:09 PM

Un plug the saw then look at the end of the motor.  In the center you will see small slot like a screw.Using a screw driver turn it about a 1/2 turn (either way).  Then plug the saw back in and try again. 

Scott, I have a similar problem ... what does turning this slot do?

Just curious... I'll try it, because I don't think it will worsen the situation.

 

 

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#5 CharleyL

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Posted January 11, 2017 - 11:11 PM

This can be caused by sawdust getting into the power switch, worn brushes in the motor, the motor worn badly and about to die completely,  problems with the electronic motor control board or a bad connection between the plug and wall socket. It's also possible, but quite unlikely that a wire inside the power cord is broken, but this usually doesn't happen unless the cord gets bent sharply at the same exact place frequently for many, many times.

 

With the power cord unplugged from the wall I would first check the brushes. These are located behind small screw caps on the front and back of the motor. Be careful, because there is a spring between the brush and cap that will make the cap try to fly away if you aren't prepared when you unscrew it. Remove the cam and slide the brush and attached out of the hole. The black carbon part of the brush should never be shorter than about 3/8". If the brush wears away and the spring touches without the brush, the motor is history. Replace the brushes before they get too short and inspect them at least every 20-30 hours of running time.

 

Next I would remove the power switch. With care, you can carefully dis-assemble it and clean it, then re-assemble it. If you can't do this, at least try blowing compressed air through it. Then re-install it. A test run will see if this was the problem. I always wrap a layer or two of electrical tape around the sides of the switch to reduce the chance of saw dust getting inside.  It still does, although it won't be necessary to clean it as often. 

 

I would also check to see that the power plug is making good connection in the wall socket when it's plugged in..

 

Also check the fuse, fuse holder, and the fuse holder cap to be certain that all of the electrical connections are good and the fuse is also good. At this point it helps to have a multi meter and understand how to use it to make simple voltage and continuity measurements., but check the above and post the progress before trying to find and use the meter.

 

Charley


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#6 bandaideman

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Posted January 12, 2017 - 01:22 AM

The above suggestions are fine.  I noted that the fuse cover was missing. Not sure when it went missing and could not find it. I did go a head and ordered a replacement fuse assembly which is how it is sold. It was a night mare in waiting for the part finding out the man who was to order it didn't. I was told the part was changed and under a different part number. I could not figure out how to replace it and took it in to the Dewalt service center and see if they could show me how it is done. Well the tech said it is different than the original and they no longer make they other one. This one will not fit in the opening. It is one unit. the tech did put it in but it hangs out and does not fasten solidly into the opening. I just had him change it back and we put a piece of elctrician tape over the opening. The brushes and fuse were fine. He felt the motor was going. Problem is that the motor is at least 250 dollars and I got the dewalt at Rockler on sale for 300 dollars. I have used it since and seems to work Ok now. I have an Ex 21 which I  used more but usually switch off every few months. Just a warning they change the outer shell and don't say anything when parts are ordered.


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#7 JTTHECLOCKMAN

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Posted January 12, 2017 - 02:59 AM

If you are using a foot switch, the first thing is disconnect and try running the saw. If still the same problem it sounds electrical. If it were mechanical the motor would sit and hum and not be able to spin. My guess would be either dust in the switch which is a common problem or a broken or loose wire somewhere in the circuit. If it stops see if you can push the arm up and down and see if it takes off. Make sure the plug is in outlet all the way and that the outlet is working fine. Plug something else in it and run it. Always start at the beginning before taking everything apart. Make sure the fuse cap is seated properly and did not vibrate loose. Report back. 



#8 Lucky2

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Posted January 12, 2017 - 03:08 AM

Ike, I thought that you still had a warranty on your saw/

Len



#9 Dan

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Posted January 12, 2017 - 03:26 AM

I had a variable speed Craftsman do just that and it was a combination of the motor blowing the motor control board. After the burial and ceremony I felt better and bought a Delta.
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#10 ike

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Posted January 12, 2017 - 03:02 PM

some of the time I can get the motor running but when I start to cut It stops and then it won't start again. I opened it and it all looked good.I took a screwdriver and turned the motor over and it was free no hang ups. If i take it to the repair shop the bill will be between #35 and $250. the motor and the current board are $250 That's 1/2 the price of a new saw.

IKE


Edited by ike, January 12, 2017 - 03:27 PM.


#11 NC Scroller

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Posted January 12, 2017 - 03:27 PM

Scott, I have a similar problem ... what does turning this slot do?

Just curious... I'll try it, because I don't think it will worsen the situation.

 

 

Tks

Larry it will do two things.  If you can't turn it at all the motor or main bearing is frozen/seized.  What you are turning is the main shaft.  Less likely there could be a bad spot on the coil (windings) and by turning it you get past it.    


Scott


#12 NC Scroller

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Posted January 12, 2017 - 03:29 PM

some of the time I can get the motor running but when I start to cut It stops and then it won't start again. I opened it and it all looked good.I took a screwdriver and turned the motor over and it was free no hang ups. If i take it to the repair shop the bill will be between #35 and $250. the motor and the current board are $250 That's 1/2 the price of a new saw.

IKE

 

Ike, put your nose near the motor.  Does it smell burnt?  If so the motor is likely toast.  It happened to me.


Scott


#13 JTTHECLOCKMAN

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Posted January 12, 2017 - 04:45 PM

some of the time I can get the motor running but when I start to cut It stops and then it won't start again. I opened it and it all looked good.I took a screwdriver and turned the motor over and it was free no hang ups. If i take it to the repair shop the bill will be between #35 and $250. the motor and the current board are $250 That's 1/2 the price of a new saw.

IKE

 

 

This sounds like an open circuit and it can be caused by vibration from the saw causing it to open or it can be from heat. The electronic board may have a cold solder joint that is causing intermediate problems. If the motor was burnt it would not run. Is the saw under warrenty??  If so do not mess with it. If not then take a good look at the electronics and look for dark areas on the board or look for loose wires. You did not mention it but I assume if you have a foot switch you did take that out of the circuit. Also you looked at the outlet Like I mentioned. Just did not know if you saw my post. 



#14 ike

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Posted January 12, 2017 - 08:56 PM

I tried all of the above-with no luck. I have a back up saw so I am not without a saw. I took it to the repair shop and they wer not sure what it is so it will cost me $36 to $260 It will be in the shop 2 to 4 weeks. I think those are the same  as anything they work on.. I still have that much left from my last craft show I am O.

IKE.



#15 CharleyL

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Posted January 12, 2017 - 09:26 PM

Not so easy come, but very quick and easy go. It's a common problem with money. 

 

I hope it's nothing serious Ike, but it could be.

 

Good luck with it.

Charley



#16 Scrolling Steve

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Posted January 13, 2017 - 12:15 AM

Sorry to hear this Ike ~.....Good luck !



#17 amazingkevin

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Posted January 13, 2017 - 03:15 AM

My DW 788 stooped running. I was cutting 3/4 popular and doing fine then the saw stopped add then started back up  thought it might be dust so I blew out every thing it ran for about 1 minute stooped then started again the stooped again for the last time. I checked the switch , fuse, and brushes all were good. I am afraid that it is the motor or the mother board. any ideas out there.

IKE

I've 7 back ups of Dewalts they all need re --greasing.luck for me.two bvwarings per Dewalt need to be pressed out.I'm sure the dill press will do the job.Let us know what the problem was.


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