# Dead Elu :(



## SamV (Nov 2, 2011)

Hello all,

A few months ago I was building some new speakers out of 18mm 13lam Birch Ply, anyways, having just turnt my Elu MOF96e off to rearrange the workpiece I turnt flicked the switch to turn it back on and nothing happend, not a sound.

I checked the fuse, I checked the cable. Since then I tried it again in case it had overheated. I got the multimeter out the other day and there's power going all the way through to the brushes. But that's where my technical expertise in such things ends.

Just now I have stripped and rebuilt it and could spot nothing obvious.











Any help or advice? Anyone in London who's able to repair? None of the tool repair shops will touch it as parts are hard to come across apparently.


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## istracpsboss (Sep 14, 2008)

Hi Sam

the parts shouldn't be that difficult. The early DeWalts were identical as they took over ELU. Try Search | Miles Tool & Machinery Centre for parts.

Cheers

Peter


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## SamV (Nov 2, 2011)

Yebbut I dunno what part. I need to find a way to diagnose.


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## Dmeadows (Jun 28, 2011)

Since you have a multimeter.. my first suggestion(while unplugged!) is make sure you have continuity thru the on/off switch in the on position. It may have dust in it!


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## SamV (Nov 2, 2011)

I have power going all the way to the brushes.

The impedance between the brushes measuring around 10-11r but only on 2 diametrically opposite points. I assume there should be more contacts on the motor?


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## Dmeadows (Jun 28, 2011)

How are you determining you have power to the brushes? If that were true and the impedance is as you say, it should be running!


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## SamV (Nov 2, 2011)

With the multimeter. Probes on each brush is showing power. Is that not right?


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## Dmeadows (Jun 28, 2011)

All pairs of opposite contacts should have continuity, and every pair should be the same! Could also be a thermal fuse imbedded in field winding. Have not looked at th shematic diagram, but I am still leaning towards the switch. The pix you posted looks like the armature and apparantly the brushes are fine!


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## Dmeadows (Jun 28, 2011)

Dmeadows said:


> How are you determining you have power to the brushes? If that were true and the impedance is as you say, it should be running!


If the router is plugged in and your are checking Voltage, that is correct. If the router is unplugged and you are measuring ohms of resistance, that will only confirm the brushes and arm are probably good.

With the router unplugged and the multimeter set for lowest ohms scale, put each lead on on side of the power switch. the meter should read VERY near zero!


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## SamV (Nov 2, 2011)

Dmeadows said:


> All pairs of opposite contacts should have continuity, and every pair should be the same! Could also be a thermal fuse imbedded in field winding. Have not looked at th shematic diagram, but I am still leaning towards the switch. The pix you posted looks like the armature and apparantly the brushes are fine!


Is each of the copper segments a contact?













Dmeadows said:


> If the router is plugged in and your are checking Voltage, that is correct. If the router is unplugged and you are measuring ohms of resistance, that will only confirm the brushes and arm are probably good.
> 
> With the router unplugged and the multimeter set for lowest ohms scale, put each lead on on side of the power switch. the meter should read VERY near zero!


It does and yes. Basically everything seems normal.


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## Dmeadows (Jun 28, 2011)

SamV said:


> Is each of the copper segments a contact?
> 
> Yes, each segment and its opposite are one coil winding of the armature. Each pair recieves power in sequence as the armature rotates. Lets go back a step or 2.
> 
> ...


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## SamV (Nov 2, 2011)

First I measured volts at the brushes and then ohms. 

Shall I remove the armature again and measure each segment? Rather than doing it via the brushes?


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## Dmeadows (Jun 28, 2011)

SamV said:


> First I measured volts at the brushes and then ohms.
> 
> Shall I remove the armature again and measure each segment? Rather than doing it via the brushes?


at the brushes..(with router unplugged!) check ohms and rotate the armature very slowly the meter reading should remain rather consitant. if it does, there is no need to dissassemble!

Without soft start/ speed control, there are actually only 5 electrical compoments in the average router(universal motor) Current comes from 1 power cord lead, thru the power switch when on, then thru the field or non-moving coil, and then thru the amature via the brushes, and back out the other power cord wire.

That is really all there is to them, electrically. Softstart/Speed control cmplicates it only slightly. The only other possibility I can think of is a thermal overload that is usually embedded in the field coil somewhere.. but if that were open you would not have voltage to the brushes!

Good luck! I am calling it a nite tonite


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## SamV (Nov 2, 2011)

First of all, the brushes are getting 238v.

In terms of resistance I'm only reading impedance (9r) here (the yellow point). When I rotate by hand I don't read anything until I'm 180 degrees.










Is the thermal overload a switch of some kind or a fuse type device?


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## Dmeadows (Jun 28, 2011)

the thermal protector is essentially an auto reset fuse.

Question.. Does the Elu have a spindle lock button for bit change? If so, there may be an interlock switch to prevent motor trying to start. Likely to be true if the spindle lock stays in lock position without holding the button. The interlock switch if exists should be 0 ohms when released.

check impedance/resistance from brushholder to brushholder.. then turn the armature slowly. if its not low here(2-30 ohms) you may have bad brushes!


That's about the only ideas I have. Best of luck!


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## SamV (Nov 2, 2011)

So the thermal fuse resets by itself?

The interlock is mechanical, no connection to anything, just a push button that locks into slots.

The brushes are brand new


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## Phil P (Jul 25, 2010)

Dmeadows said:


> Question.. Does the Elu have a spindle lock button for bit change? If so, there may be an interlock switch to prevent motor trying to start. Likely to be true if the spindle lock stays in lock position without holding the button. The interlock switch if exists should be 0 ohms when released.


Yes it does, but it is merely a mechanical sprung pin type device. There are no electrical connections in it

Thanks for your insight into electrical motors, BTW

Regards

Phil


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## SamV (Nov 2, 2011)

So now that we've had a few years to think on it, any new ideas for what could be wrong?


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## JCJCJC (May 15, 2012)

SamV said:


> So now that we've had a few years to think on it, any new ideas for what could be wrong?


I rebuilt an Elu that looked a lot worse than yours. Take the opportunity to note the bearing numbers while you have it apart, in case you ever need them. I would try bypassing the on/off switch and then plug it in and see if it runs. My next resort would be a place that rewinds motors, they have the rest equipment to easily find faults in the armature or field windings.

Jc


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## ydna (Mar 7, 2012)

The elu 96 is well known for having switch issues


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## DaninVan (Jan 1, 2012)

Just spit-balling here, but you've confirmed that the cord plug and the wall receptacle are both 100%? 
Power tool cord conductors and their plugs are always suspect due to the constant bending and twisting.
Too obvious I know, but assume nothing...


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## oldyam (Aug 2, 2015)

Hi Sam

Before you go off checking everything else .......

In your post no 14 you show a pic of the armature installed and the fact that the armature only shows a resistance value at one point on its rotation ....... You have found your fault the armature is faulty !!!

Each pair of commutator segments should show an identical reading across the winding for the motor to function. Unless the brushes are somehow lifted off the commutator segments ( ie by the seperators between the copper segments standing proud of the copper ) then there should be continuity across them.

Just to be sure its not tarnishing / burning etc I would lightly rub the commutator with abrasive paper until the copper is bright again ( you can do this by hand wrap the abrasive around the commutator and rotate the whole armature to polish off any tarnish. A quick check round with a multimeter on ohms checking segments 180 degrees apart will tell if there is any continuity, if not its a new armature that is required.

The fact that you have continuity from the mains plug to the motor brushes means that you have continuity through the stator windings if they are in series with the brushes.

Good luck with your investigations


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