Bosch Router fault, lots of sparks, faulty armature?

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tin...@isbd.co.uk

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Aug 26, 2007, 5:02:43 AM8/26/07
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I posted recently about both my routers (a Bosch GOF1300 ACE and a
Ferm cheapie from Screwfix) failing with apparently worn/crumbled
brushes.

Well new brushes for the Ferm (it is the same as the Trend T3) fixed
that but new brushes for the Bosch didn't help at all.

So, what has gone wrong with the Bosch and is it worth fixing? The
symptoms are lack of power/speed and lots of sparking from the
brushes. Does this indicate an armature insulation failure between
windings? Is it possible to test for this? If it's of any
significance the failure was quite sudden, the router ran quite
happily for several minutes when I started using it last week and then
suddenly lost power, ran slowly and there were lots of sparks around
the commutator/brush contact.

Any ideas or suggestions would be welcome, I'd want to be very sure
that it's a failed armature before replacing it. ... in fact if it
is the armature that has failed a replacement costs significantly more
than a complete new router, I just looked it up.

--
Chris Green

Weatherlawyer

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Aug 26, 2007, 5:29:13 AM8/26/07
to

What voltage was the router?

If it was intended for 110 volt use and you just changed the plug, you
blew it.

If there was some fault with the armature then you should get it
replaced.


John Rumm

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Aug 26, 2007, 1:55:15 PM8/26/07
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tin...@isbd.co.uk wrote:

> So, what has gone wrong with the Bosch and is it worth fixing? The
> symptoms are lack of power/speed and lots of sparking from the
> brushes. Does this indicate an armature insulation failure between
> windings? Is it possible to test for this? If it's of any

Sounds that way.

> Any ideas or suggestions would be welcome, I'd want to be very sure
> that it's a failed armature before replacing it. ... in fact if it
> is the armature that has failed a replacement costs significantly more
> than a complete new router, I just looked it up.

What sort of Bosch is it? Usually with the pro tools the spares can be
quite cost effective compared to the whole tool. For the green ones its
more pot luck.

You could try:

http://www.healystool.co.uk/

--
Cheers,

John.

/=================================================================\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\=================================================================/

tin...@isbd.co.uk

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Aug 26, 2007, 2:13:15 PM8/26/07
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No, I'm not quite that stupid, or at least not normally! :-)
It's a 240V router and I hadn't changed anything on it, just dug it
out of its drawer and started using it.


> If there was some fault with the armature then you should get it
> replaced.
>

It's well over 5 years old so no warranty/guarantee.

--
Chris Green

tin...@isbd.co.uk

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Aug 26, 2007, 2:29:59 PM8/26/07
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John Rumm <see.my.s...@nowhere.null> wrote:
> tin...@isbd.co.uk wrote:
>
> > So, what has gone wrong with the Bosch and is it worth fixing? The
> > symptoms are lack of power/speed and lots of sparking from the
> > brushes. Does this indicate an armature insulation failure between
> > windings? Is it possible to test for this? If it's of any
>
> Sounds that way.
>
> > Any ideas or suggestions would be welcome, I'd want to be very sure
> > that it's a failed armature before replacing it. ... in fact if it
> > is the armature that has failed a replacement costs significantly more
> > than a complete new router, I just looked it up.
>
> What sort of Bosch is it? Usually with the pro tools the spares can be
> quite cost effective compared to the whole tool. For the green ones its
> more pot luck.
>
It's a blue Bosch GOF1300ACE, a replacement armature from
http://www.mtmc.co.uk/ is £162.15 which is a whole lot more than quite
a few 1/2" routers available nowadays. I think the GOF1300ACE is a
model that Bosch no longer make.


> You could try:
>
> http://www.healystool.co.uk/
>
>
>
> --
> Cheers,
>
> John.
>
> /=================================================================\
> | Internode Ltd - http://www.internode.co.uk |
> |-----------------------------------------------------------------|
> | John Rumm - john(at)internode(dot)co(dot)uk |
> \=================================================================/

--
Chris Green

meow...@care2.com

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Aug 26, 2007, 4:04:58 PM8/26/07
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tinn...@isbd.co.uk wrote:

Why not test it and see. A multimeter wont pick up all faults, but it
will some.
Clean carbon despots from between the commutator segments first.

Damaged armatures can be bodged to make them run, and its an option
tha can work happily enough, so worth considering..


NT

Pete C

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Aug 26, 2007, 4:13:12 PM8/26/07
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Hi,

Might be worth a call to Bosch, explain it's a blue pro model with
light use and see what they say.

Failing that look for a local motor rewinding co, I'd expect they can
at least diagnose it for a small fee.

cheers,
Pete.

John Rumm

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Aug 26, 2007, 4:17:54 PM8/26/07
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tin...@isbd.co.uk wrote:

> It's a blue Bosch GOF1300ACE, a replacement armature from
> http://www.mtmc.co.uk/ is £162.15 which is a whole lot more than quite
> a few 1/2" routers available nowadays. I think the GOF1300ACE is a
> model that Bosch no longer make.

Yup at that price it is not worth it since you could have a Freud
FT2000E or similar for that.

(Quite often armatures work out at £30-£40 which is far more reasonable
repair price).

meow...@care2.com

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Aug 26, 2007, 6:12:51 PM8/26/07
to

Rewind may be cheaper too.


NT

Bob Martin

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Aug 27, 2007, 3:45:22 AM8/27/07
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I had something similar - turned out to be a piece of metal had got inside
via the ventilation slots.

tin...@isbd.co.uk

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Aug 28, 2007, 11:21:11 AM8/28/07
to
meow...@care2.com wrote:

> tinn...@isbd.co.uk wrote:
>
> > So, what has gone wrong with the Bosch and is it worth fixing? The
> > symptoms are lack of power/speed and lots of sparking from the
> > brushes. Does this indicate an armature insulation failure between
> > windings? Is it possible to test for this? If it's of any
> > significance the failure was quite sudden, the router ran quite
> > happily for several minutes when I started using it last week and then
> > suddenly lost power, ran slowly and there were lots of sparks around
> > the commutator/brush contact.
> >
> > Any ideas or suggestions would be welcome, I'd want to be very sure
> > that it's a failed armature before replacing it. ... in fact if it
> > is the armature that has failed a replacement costs significantly more
> > than a complete new router, I just looked it up.
>
> Why not test it and see. A multimeter wont pick up all faults, but it
> will some.
> Clean carbon despots from between the commutator segments first.
>
Er, yes, but what do I test? That was part of my original question,
using a multimeter what sort of resistance values should I expect?
Does the armature comprise a load of separate windings each of which
goes from one commutator 'bar' to another? If so I would expect all
commutator 'bars' to be unconnected except for the one at the other
end of the particular winding, is this correct? I'm quite happy to
spend a little time and effort on this and have two multimeters, can
solder, etc.

> Damaged armatures can be bodged to make them run, and its an option
> tha can work happily enough, so worth considering..
>

I'm considering it! :-)

--
Chris Green

meow...@care2.com

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Aug 28, 2007, 4:19:47 PM8/28/07
to
tinn...@isbd.co.uk wrote:
> meow...@care2.com wrote:
> > tinn...@isbd.co.uk wrote:

> > Why not test it and see. A multimeter wont pick up all faults, but it
> > will some.
> > Clean carbon despots from between the commutator segments first.

> Er, yes, but what do I test? That was part of my original question,
> using a multimeter what sort of resistance values should I expect?
> Does the armature comprise a load of separate windings each of which
> goes from one commutator 'bar' to another? If so I would expect all
> commutator 'bars' to be unconnected except for the one at the other
> end of the particular winding, is this correct? I'm quite happy to
> spend a little time and effort on this and have two multimeters, can
> solder, etc.

OK, the commutator has several segments, and there are several
armature windings, each one connected between 2 commutator
segments.

A multimeter can pick up:
- a difference in R of one winding from the others
- any conduction from armature to the rotor.

The simplest way to test it is to put the meter across the mains
plug pins (NOT plugged in), and turn the tool round very slowly so
you see the R of each section of the motor armature. Analogue
meters are much easier to use for this.

Comparing Rs wil pick up some faults, though not all. If this
doesnt work you'll need to compare L values rather than R, as L
nosedives with a shorted turn or 2, whereas R can stay almost the
same. Its easiest to do this by connecting the tool in series
with a lightbulb, and putting the pair across a low voltage ac
supply, eg 12v. Measuring the voltage across the tool will show
up a bad winding section as the motor is turned. The lightbulb's
non-linearity accentuates the fault. Your psu v needs to be low
enough that the tool doesnt spin.


> > Damaged armatures can be bodged to make them run, and its an option
> > tha can work happily enough, so worth considering..
> >
> I'm considering it! :-)

Despite the bodginess, motors run very close to full speed with
one (faulty) winding section disconnected. If the section is
identified, the section's 2 wires can simply be snipped to
disconnect it. Its not ideal, but where a tool will retain almost all
its utility, and would cost almost as much as a new one to fix,
such a trick can become a sensible option.


A much bodgier option, which I really dont recommend, but used
to do years ago, is to put a partially shorted motor in series with
a ballast of some kind (eg a 3kW heater). This enables shorted
motors to run. The motor will never reach full speed like that, and
they do run hot. So not a great option, but one anyone can do
easily if stuck, and it can easily resurrect kit thats not worth a
proper repair, hence its effectively a way to get free tools.


NT

tin...@isbd.co.uk

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Aug 29, 2007, 8:08:52 AM8/29/07
to
meow...@care2.com wrote:
> tinn...@isbd.co.uk wrote:
> > meow...@care2.com wrote:
> > > tinn...@isbd.co.uk wrote:
>
> > > Why not test it and see. A multimeter wont pick up all faults, but it
> > > will some.
> > > Clean carbon despots from between the commutator segments first.
>
> > Er, yes, but what do I test? That was part of my original question,
> > using a multimeter what sort of resistance values should I expect?
> > Does the armature comprise a load of separate windings each of which
> > goes from one commutator 'bar' to another? If so I would expect all
> > commutator 'bars' to be unconnected except for the one at the other
> > end of the particular winding, is this correct? I'm quite happy to
> > spend a little time and effort on this and have two multimeters, can
> > solder, etc.
>
> OK, the commutator has several segments, and there are several
> armature windings, each one connected between 2 commutator
> segments.
>
OK, that's what I thought (and my poor description above was trying to
say).

> A multimeter can pick up:
> - a difference in R of one winding from the others
> - any conduction from armature to the rotor.
>
> The simplest way to test it is to put the meter across the mains
> plug pins (NOT plugged in), and turn the tool round very slowly so
> you see the R of each section of the motor armature. Analogue
> meters are much easier to use for this.
>

OK, I have an analogue meter as well as a digital one, I'll try this
and see what I get.

> Comparing Rs wil pick up some faults, though not all. If this
> doesnt work you'll need to compare L values rather than R, as L
> nosedives with a shorted turn or 2, whereas R can stay almost the
> same. Its easiest to do this by connecting the tool in series
> with a lightbulb, and putting the pair across a low voltage ac
> supply, eg 12v. Measuring the voltage across the tool will show
> up a bad winding section as the motor is turned. The lightbulb's
> non-linearity accentuates the fault. Your psu v needs to be low
> enough that the tool doesnt spin.
>

Very clever! :-)

>
> > > Damaged armatures can be bodged to make them run, and its an option
> > > tha can work happily enough, so worth considering..
> > >
> > I'm considering it! :-)
>
> Despite the bodginess, motors run very close to full speed with
> one (faulty) winding section disconnected. If the section is
> identified, the section's 2 wires can simply be snipped to
> disconnect it. Its not ideal, but where a tool will retain almost all
> its utility, and would cost almost as much as a new one to fix,
> such a trick can become a sensible option.
>

If it is a failed winding then this would seem to be a sensible
approach.

Thanks for the very complete and helpful explanation, I'll report the
results of my examination/repair in due course.

--
Chris Green

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