# deWalt DW 621- dead.



## MascaraSnake (Jul 26, 2010)

Hi- my lovely trusty DW 621 has suddenly stopped working. I managed to get it going infrequently by a firm tap on either side with a hammer (where I thought brushes likely reside). So this implied -possibly- was indeed brushes, an easy fix. But now its totally dead, not even a fraction of a second working at all. 

Brushes out & certainly don't look new, being maybe 1/3rd of length of new ones, one maybe even 1/4 as long.. but the springs clamp them both (call them 1cm left of the graphite block each) still firmly it seems against armature & I can see them rubbing when I twist the spindle ok.

Any ideas? Thanks M. Snake.


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## Nickp (Dec 4, 2012)

Dirty/dusty switch...?


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## Cherryville Chuck (Sep 28, 2010)

Switch is a good possibility like Nick says. It's an easy test if you know a bit like it sounds you do. Just put a jumper across the in and out wires on it and see if it fires up.


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## Herb Stoops (Aug 28, 2012)

If Charles idea doesn't work,look at the brushes.

Intermittent running sounds like brushes to me,Especially if you can tip it or bump it and it will try to start. 

Herb


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## greenacres2 (Dec 23, 2011)

Just a question for my future learning---if it is brushes, which means that it's been used enough to wear the brushes that far, might it make sense to pull and clean the armeture? If so, bearings replacement while it's apart?? Or is just putting a set of brushes in a normal practice??

Thanks!!
earl


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## Quillman (Aug 16, 2010)

Definitely agree (over use) with GreenA. Machine due for replacement or gross overhaul.


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## Stick486 (Jan 4, 2013)

greenacres2 said:


> Just a question for my future learning---if it is brushes, which means that it's been used enough to wear the brushes that far, might it make sense to pull and clean the armeture? If so, bearings replacement while it's apart?? Or is just putting a set of brushes in a normal practice??
> 
> Thanks!!
> earl


go w/ the normal...


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## Cherryville Chuck (Sep 28, 2010)

If you can find the right supplier bearings are fairly cheap, as in about $10 each.


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## TenGees (Sep 12, 2012)

*Not Recommended Brush Test*

I was given a Makita drill that didn't work properly... slow, intermittent and gutless. I didn't know if it was worth investing in parts. Thinking it might just be brushes, I carved a couple of brush 'extensions' out of carpenters pencil lead. This added about about an eighth of an inch to the length of the brushes. When this improved the performance, I knew it was the brushes. It turned out that the brushes only cost the equivalent of two large coffees anyway. Had I known that I could've just bought the brushes and saved myself some work.

When I replaced the brushes I also carefully cleaned the comm up a bit with sandpaper and blew out the crap. The drill works like new now... my most-used corded drill.

Moral: If you suspect the brushes and they're cheap, just buy a set and try it.


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## MascaraSnake (Jul 26, 2010)

Hi chaps- thanks for replies, only just aware of them all. Grateful.

Now I checked switch- fine, and am quizzing the brushes as one might. Ive orddered some (had to instigate the most likely parts on their way/ I make a living with this router, but cant afford a deWalt service, and Ive repalced brushes on a cheaper router before with ~ similar'ish symtoms) so fingers crossed just that.

But it might be the control unit (is the other fallible part of these dw621 routers, from www spiel afaict). Some folks mentioned you can test this by bypassing it with a couple of appropriate wires.. but without knowing exactly what Im doing/ which wires to connect to bypass Im not proceeding.. unless with help here. Its a simple thing to do sure, but one that could kill the router if I apply wrong.

Anyone bypassed a control unit before?


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## Nickp (Dec 4, 2012)

I use a pink eraser to clean the surface before installing new brushes...unless it's scored...then clean it up with contact cleaner then a shot of air. If you've taken it this far, check the mating surfaces to make sure the radii match...

Stick's pdfs are a good read...


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## Cherryville Chuck (Sep 28, 2010)

Snake you could look up the posts of Dmeadows (I think that`s how his user name reads). He was a repairman for many years and I`ve seen him give advice on it before. Find him in our members list and click on his personal profile. Once there ther is a menu bar with the first word Statistics. When you click on that it gives you an option to see all of the posts he has made. Go through them and look for thread titles about control module issues. If it is a really simple module it will only have 2 wires but some also had sensing circuits built in and I don`t know how they work.


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## MascaraSnake (Jul 26, 2010)

Hi CherryChuck- thanks thats great/ will do.

Really need to sort this- I've put in new brushes.. no joy. Waste of £14 there then.

I need to find out A) how to bypass the control unit to test it works like so (so then control unit defo the prob), and B) whether a series 2 control unit is same, or fits ok a series 1 (mine). Three damn series look identical but some parts fractionally different- most annoying.

Thanks M.Snake.


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## Nickp (Dec 4, 2012)

MascaraSnake said:


> Hi CherryChuck- thanks thats great/ will do.
> 
> Really need to sort this- I've put in new brushes.. no joy. Waste of £14 there then.
> 
> ...


Is your speed controller 2-wire...? If so, it's likely to only interrupt the main power to the brushes (in series between power and hot brush). The speed control is also likely to be integrated in the cap so no extra wires for that. 

If that is the case, you should be able to literally bypass the controller by coming out of the switch and wiring to the hot brush.

This will leave you with no speed control and will need external speed controller...you will also lose soft-start.

Please verify all this before attempting any re-wiring...


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## Stick486 (Jan 4, 2013)

MascaraSnake said:


> Hi CherryChuck- thanks thats great/ will do.
> 
> Really need to sort this- I've put in new brushes.. no joy. Waste of £14 there then.
> 
> ...


here...


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## MascaraSnake (Jul 26, 2010)

Nickp said:


> Is your speed controller 2-wire...? If so, it's likely to only interrupt the main power to the brushes (in series between power and hot brush). The speed control is also likely to be integrated in the cap so no extra wires for that.
> 
> If that is the case, you should be able to literally bypass the controller by coming out of the switch and wiring to the hot brush.
> 
> ...


Ok I get the idea I think.

Yes it seems only 2 wires: Powercord 2 wires > switch > control module > then it seems c/m has 2 "female/ out" terminals adjacent to each other on a protruding stem.. which press-connect to 2 "male" terminals sticking up from the top of the main yellow DW body.

So, it seems logical to disconnect the c/m stem with both its female connects in, then connecting from the 2 sides of the switch each, run a wire each to these 2 body male terminals.. bypassing the c/m. 

Or run a wire from each side of the switch directly to each side of the brushes? I guess ^ this is the same thing? (If so there should be continuity between the two "male" body terminals, no?). 

But I must make 100% sure 1st. I will not even attempt until Im 110% sure. I dont want to fry this lovely machine, or my nuts thanking you very please.

Cheers, MS.


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## MascaraSnake (Jul 26, 2010)

The two terminals in the yellow body (that the control module connect to, via the c/m's protruding stalk on the RHS here) Ive marked with a tape mark 'V'


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## MascaraSnake (Jul 26, 2010)

Stick486 said:


> here...


Very grateful for the links- read them all.

Switch/ seems very good. 
Brushes / new (solid continuity between them). 
Commutator section/ looks clean, no signs of anything bad, all strips shiny none missing (looks nr new). 
Armature wires/ no sign of burnt or discolouration of wires. 
Armature bearings/ seem fine, spins nice and freely.

I cant see much of the field to check, or know what these two "male" terminals are exactly the c/m plugs into. I find no continuity between them, but I find one has continuity to its nearer brush. Other termilal has neither continuity to its nearer brush, nor to the other terminal. Switch closed for this.

Any help much appreciated- my livelihood depends on this machine, and I cant afford the time (esp at xmas) or money for a deWalt service.

Thanks for reading my spiel- MS.


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## Stick486 (Jan 4, 2013)

MascaraSnake said:


> Commutator section/ looks clean, no signs of anything bad, all strips shiny none missing (looks nr new).
> 
> Thanks for reading my spiel- MS.


clean between the commutator bars w/ a tooth pick..
by pass the speed controller.......


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## MascaraSnake (Jul 26, 2010)

Stick486 said:


> clean between the commutator bars w/ a tooth pick..
> by pass the speed controller.......


Will clean between the bars for sure then.

This bypass is what Im trying to find out how to do/ why I added the pic.

This dw621 has a reputation so I read, for the control module failing (what I guess you referring to re the speed controller?).

Does anyone know how?


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## MascaraSnake (Jul 26, 2010)

Stick486 said:


> clean between the commutator bars w/ a tooth pick..
> by pass the speed controller.......


Cleaned between- nothing.

I do get very occasional signs of life, just now on for 1 sec for eg/ thats it. Then a pulse but not even a sec, thats about it. Totally dead.


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## Stick486 (Jan 4, 2013)

MascaraSnake said:


> 1... Will clean between the bars for sure then.
> 
> 2... This bypass is what Im trying to find out how to do/ why I added the pic.
> 
> ...


1.... be genteel and polite..
2.... got a schematic...
3.... yes.. one in the same..


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## MascaraSnake (Jul 26, 2010)

Stick486 said:


> 1.... be genteel and polite..
> 2.... got a schematic...
> 3.... yes.. one in the same..


Been polite with the commutators. Ive scoured the www for an hour for a schematic but none out there.

Can anyone help? has anyone bypassed a router control unit?


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## Stick486 (Jan 4, 2013)

MascaraSnake said:


> Been polite with the commutators. Ive scoured the www for an hour for a schematic but none out there.
> 
> Can anyone help? has anyone bypassed a router control unit?


I see there are DW621 type 1,2 and 3 routers if that means any thing..

Search : eReplacementParts.com


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## Nickp (Dec 4, 2012)

Ms...if both wires of the controller go to the males then removing the controller is opening the circuit...that would mean a jumper across the two males would close the circuit from the switch to the hot brush.

To verify, one of the males should be connected to the switch and the other to the hot brush.

Do not connect the two wires from the switch to anything...the switch should only be opening n closing only the hot lead from the power cable...


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## MascaraSnake (Jul 26, 2010)

Stick486 said:


> I see there are DW621 type 1,2 and 3 routers if that means any thing..
> 
> Search : eRepacementParts.com


I wish I had your eagle eyes- assumed just one and bought the brushes (didnt fit) and a dust guard (doesnt fit). I resoldered the brush terminals w'my olduns and ok tho.

Its v. annoying this 3 series of 621: minute diffferences in these two parts I bought suggests if I found a donor 621 (I have, spares/ repairs £50 with c/unit & switch "work fine") the c/u might not fit by a fraction too.

Mine's a series 1, this donor machine series 2.


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## MascaraSnake (Jul 26, 2010)

Nickp said:


> Ms...if both wires of the controller go to the males then removing the controller is opening the circuit...that would mean a jumper across the two males would close the circuit from the switch to the hot brush.
> 
> To verify, one of the males should be connected to the switch and the other to the hot brush.
> 
> Do not connect the two wires from the switch to anything...the switch should only be opening n closing only the hot lead from the power cable...


Hi NickP- yes this is what I was thinking too/ makes logical sense.. but unless Im 110% sure etc etc.

One of these males reads continuity to its nearer brush (the *upper* one in the pic above: I marked these males with a V and two black marks inside the yellow shell). 

*Other male tho does -not- read continuity to the other brush (*lower* in pic).. as I was expecting.

*Does that seem correct to you? is that to be expected-?

thanks MS


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## Stick486 (Jan 4, 2013)

MascaraSnake said:


> I wish I had your eagle eyes- assumed just one and bought the brushes (didnt fit) and a dust guard (doesnt fit). I resoldered the brush terminals w'my olduns and ok tho.
> 
> Its v. annoying this 3 series of 621: minute diffferences in these two parts I bought suggests if I found a donor 621 (I have, spares/ repairs £50 with c/unit & switch "work fine") the c/u might not fit by a fraction too.
> 
> Mine's a series 1, this donor machine series 2.


found this....

.





is this your module???
where do the switch wires hook to...
where does he module hook up at and what color are the wires...

.


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## Stick486 (Jan 4, 2013)

is the thumb wheel on the controller free turning...


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## Stick486 (Jan 4, 2013)

having a spare router or two sure would be nice....


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## MascaraSnake (Jul 26, 2010)

Hi Stick-

yup thats my fella. And yup that looks like the c/unit even the wires same colour. 

The clip just shows the top of the c/unit, alas his fix was only a glue job.. lucky blighter. I did see this 1st off but not actually any info there to help either refit a new c/u, or prior to that (& what Im specifiacally wanting to do here) is test the old one -IS- where the prob resides 1st, by bypassing it.

Ok on the black new c/u unit pic above. The grey / purple long wires attatch to either side of switch. The c/u has 2 exit points: these in the pic above are low RHS, in the middle, together (on end of a protruding 'stalk' 2 female terminals adjacent in the end). You can see this 'stalk' on my pic (on pg 2) sticking up prominantly twds the RHS.


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## MascaraSnake (Jul 26, 2010)

Stick486 said:


> is the thumb wheel on the controller free turning...


Yes thumb wheel spins, no evidence this is the cause (tho if it was, its integral to the c/u anyway).

I think it points to either of 4 things: the c/u (a cap or maybe the wheel pot/ or s'thing in the circuit- any bit of which cannot be replaced).. the 'field' tho Im not sure how on earth you'd test this or get it out to replace.. the armature (main part, or the commutator section).. or a connection between the c/u and the next bit along the chain (the 'field'?) or a connection between other sections.

So if Ive ruled out switch, brushes, the next port of call is the c/u. Its just a Q of how to bypass it to test if, it is indeed that.


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## MascaraSnake (Jul 26, 2010)

Stick486 said:


> having a spare router or two sure would be nice....


Yup. But the spares/ repairs one available, even with c/u and switch "these work fine" is a series 2. Mine's a series 1. With the minute differeces with my brushes & placcy guard I bought (actually a series 3).. even as I am fairly sure, I cannot be certain enough the c/u will fit.


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## Nickp (Dec 4, 2012)

MascaraSnake said:


> Hi NickP- yes this is what I was thinking too/ makes logical sense.. but unless Im 110% sure etc etc.
> 
> One of these males reads continuity to its nearer brush (the *upper* one in the pic above: I marked these males with a V and two black marks inside the yellow shell).
> 
> ...


Yes...check to make sure it has continuity to the switch...

Power hot to switch to male to jumper to other male to brush...


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## MascaraSnake (Jul 26, 2010)

Nickp said:


> Yes...check to make sure it has continuity to the switch...
> 
> Power hot to switch to male to jumper to other male to brush...


Ok this is what I see..


Power hot to switch= fine.

Switch to male terminal = no continuity.

Other male terminal to one brush = fine.


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## Stick486 (Jan 4, 2013)

did you bypass the switch???


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## Nickp (Dec 4, 2012)

MascaraSnake said:


> Ok this is what I see..
> 
> 
> Power hot to switch= fine.
> ...


..you may have bad connection between out of switch to in of male...


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## MascaraSnake (Jul 26, 2010)

Nickp said:


> ..you may have bad connection between out of switch to in of male...


Both sides of switch do not connect to this (or either for that matter) male terminals on the body.

Do you know what would lie _*between*_ the switch and this terminal?? (presumably the other terminal just connects to one brush, as it tests connected to one only). IE part of the router circuit (IE such as the 'field').. or would it just be a wire from the switch to this terminal without any component between it?

Are you sure this, or either terminal should definitely connect to the switch directly if I DMM between them?


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## Nickp (Dec 4, 2012)

MS...sorry for the crude drawing but wanted to make sure we're on the same page, so to speak...

first, make sure the switch works...continuity check across the two switch terminals, turn switch on and off...works...?

...check physical connections of wires, for example, if the two males are mounted on a board, the joint underneath may be faulty (i.e. cold solder joint) or maybe the crimp is bad. physically place ohmmeter on the wire and then on the component...does each of the connections show continuity consistently...? even while jiggling the wires...?

The offending piece of the puzzle right now is not having continuity between the out of the switch and the in of M1 (on my drawing)...can you do a physical check of all connections, specifically, the mail spade...?

In doing so, wouldn't it be great if a bad connection is found and the controller has been good all along...but...

assuming all physical wire connections are good, jumping M1 to M2 should do the trick. Just remember, the router will run at full speed until you put an external speed control.

For trouble shooting, I would leave one end of your meter to the hot side of the power cord and use the other lead to chase the circuit, one connection at a time...is that doable...?

If you find a bad connection I would then remount the controller prior to jumping it out...


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## MascaraSnake (Jul 26, 2010)

Hi Nick,

followed all that (terrific thanks, & a pic I understand clearly) and thats how I thought it configured, so the bypassing would be a Q of simply jumpering across the two M1 to M2.

Ive done exactly as you suggest, and ruled out any wire below M1, jiggled and wiggled all relevant bits. DMM shown not a sausage between Sw and M1.

It seems logical as you say, to think that I should see continuity between SW and M1. As Im not I need to know what (as would 99% likely be same on all routers) component is situated between Sw and M1 usually.

Is it the field??


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## Nickp (Dec 4, 2012)

MascaraSnake said:


> Hi Nick,
> 
> followed all that (terrific thanks, & a pic I understand clearly) and thats how I thought it configured, so the bypassing would be a Q of simply jumpering across the two M1 to M2.
> 
> ...


No...field, armature, etc...are all part of motor and case.

Just to be clear...you followed continuity through to the other side of the switch and can see the switch make and break continuity...right...?

And then you go to M1 and no longer see the action of the switch or continuity...?

and you are able to see under M1 to make sure the wire is a good connection to the M1 terminal...? crimped or soldered...?


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## Nickp (Dec 4, 2012)

@MascaraSnake

...sent you a PM...


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## MascaraSnake (Jul 26, 2010)

Nickp said:


> No...field, armature, etc...are all part of motor and case.


But they are not connected together are they when it is not powered (I mean electrically connected, not just physically connected)-?



Nickp said:


> Just to be clear...you followed continuity through to the other side of the switch and can see the switch make and break continuity...right...?


I can see the switch is 100% fine. Power cords + and - go in, each makes an A+ connection with its corresponding other side of switch, from where two wires lead into the c/unit.

This actually differs from your diagram then: I have both wires + an - going into the c/unit straight from the switch. The + connects to one of the c/unit's terminals (one of the two adjacent exit points on the c/u which connect to M1 or M2 on the body).. the - wire just goes into the c/u: it doesnt connect to the c/u other terminal.



Nickp said:


> And then you go to M1 and no longer see the action of the switch or continuity...?
> 
> and you are able to see under M1 to make sure the wire is a good connection to the M1 terminal...? crimped or soldered...?


So there is a break now as the c/unit is lifted off from its terminals M1 and M2. Ive wiggled and giggled under M1 and still no connection to the switch.

Im still unsure about whether M1 should be connected to the switch (with the c/u lifted off, like my photo pg2).. and whether there is something that has failed between M1 and SW.. _or whether the c/u makes this connection when inserted back on._


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## MascaraSnake (Jul 26, 2010)

Hi Nick- Switch is defo 100& fine. Let me just simplify what's what:



2 power cords > switch > 2 exit > both go into c/unit > both exit via the c/u terminals.

C/u terminals join onto the M1 and M2 body terminals. I have the c/unit lifted off from the body, like photo.

------------------------------------------------------------------------------------------------------

Continuity +: power cord > switch (then goes into c/unit) > c/unit exit terminal.
Continuity -: power cord > switch (then goes into c/unit)..

Continuity across the brushes.
Continuity between one M terminal, and one brush.

------------------------------------------------------------------------------------------------------

No continuity: between the other M terminal and anything at all (nothing between it and the Switch for eg).


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## Nickp (Dec 4, 2012)

*2nd picture...*

Ms...I see...a different picture, then.

So... the controller's two wires are normally connected to the two male terminals...?

and you say the + and - of the power cord both go to the switch ( 4 poles) and + and - of switch then plug directly onto something else on the controller...? and the controller's two wires go directly M1 and M2...? (see attached)

...and only one of the two Male terminals go to one of the brushes...?

...can you tell where the wire from the other brush connects to...?


EDIT...if the above is true, it would appear M1 is somehow severed from the cold (return) brush....ultimately, power needs to go in the hot brush and come out the cold neutral brush...


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## MascaraSnake (Jul 26, 2010)

Your pic seems more accurate yes. I am now measuring stuff with the controller in place/ I can just get to M1 and M2 like so.

The two wires from the switch go to the controller. Two wires exit the the controller, and join the body at the junction of M1 and M2.



From the power plug +, I read continuity right the way thru, via the controller, to M1.

From the power -, I read continuity thru to the switch (router side), IE the switch is closed/ and works.




I only see continuity between two other sets of points: across the brushes (expected), and between the M2 and one brush. 

(Can you see my photo on page 2?)


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## MascaraSnake (Jul 26, 2010)

Nickp said:


> ...and only one of the two Male terminals go to one of the brushes...?


Yes correct.



Nickp said:


> ...can you tell where the wire from the other brush connects to...?


Alas I cannot see where either brushes go- nothing visible apart from themselves connecting across the armature. I do read though, that one brush connects to M1.


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## MascaraSnake (Jul 26, 2010)

M1 connects to one brush


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## MascaraSnake (Jul 26, 2010)

And (with the switch closed) the other M2 does not connect to plug+ (or plug- / same/ checked these two countless times)..


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## Nickp (Dec 4, 2012)

...Does the "open" brush show continuity to the neutral/return anywhere...power plug, switch, input to controller, frame...?

Logically, if the controller is in series with both power and neutral between switch and brushes (back to original question about bypass) the output of the controller should go to each of the brushes. 

If one were to take out everything and connect hot to brush and neutral to other brush, the motor would spin at full RPM. My guess is that since there is no connection between M1 and the other brush, the motor cannot energize...

The break in the circuit must logically be between M1 and the other brush. It is very likely that the problem might not be in the controller but rather between M1 and the brush...as you have measured with the DMM...

...time to get more physical...I think you need to find where the other brush's wire goes to...or where it should...

Just to clarify...I've been referring to the M-terminal that does have a connection to a brush as M-2...hope that hasn't caused confusion...


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## MascaraSnake (Jul 26, 2010)

Nickp- (I say tentatively).. ITS FIXED!

I ripped it apart (after a YTube clip of a dw625 showed me how he prized off the top spinny magnet from the aramature top- which I v minor damaged top of shaft of, or the tiny ceramic washer in top of/ no big deal I'll araldite if needs be) and then hadnt a clue what I was doing once all apart.. panic, no sign of anything amiss, couldnt get the field section out.. so just scratched a few contacts clean whilst there, a bit of an air dust blast & shoved it back together thinking I now need buy another. Tried it.. works!

No sign of intermittent on/off, speed control works all speeds, soft start.. exactly as always.

major fingers crossed/ could be its last legs breath.. but who knows?!

Huge help Nick, seriously Im mighty grateful/ wouldve given up if you hadnt spurred me on. Thanks RC


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## Nickp (Dec 4, 2012)

Your very welcome...good luck with it...


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