Posted here a while ago broken speed control: Well they sent me a new
one - no charge! but the damn thing still won't work. The motor just hums in
all positions of the control. I measured 100VDC going to 2 of the 4 wires to
the motor. The motor bearings and brushes look good. Any ideas what further
diagnosis I could pursue?

"Martik" wrote in message
news:jeIHd.36644$06.34415@clgrps12...
Posted here a while ago broken speed control: Well they sent me a new
one - no charge! but the damn thing still won't work. The motor just hums
in
all positions of the control. I measured 100VDC going to 2 of the 4 wires
to
the motor. The motor bearings and brushes look good. Any ideas what
further
diagnosis I could pursue?



There's 4 wires to the motor? I had assumed the brushes would be in series
with the field coil, you need voltage to both pairs of wires for the motor
to run.

"James Sweet" wrote in message
news:zy%Hd.13338$Os6.4292@trnddc08...

"Martik" wrote in message
news:jeIHd.36644$06.34415@clgrps12...
Posted here a while ago broken speed control: Well they sent me a new
one - no charge! but the damn thing still won't work. The motor just hums
in
all positions of the control. I measured 100VDC going to 2 of the 4 wires
to
the motor. The motor bearings and brushes look good. Any ideas what
further
diagnosis I could pursue?



There's 4 wires to the motor? I had assumed the brushes would be in series
with the field coil, you need voltage to both pairs of wires for the motor
to run.

The 2 wires to the brushes have the 100VDC, I do not know what the others
are for.

Here is a picture, the red and blue wires go to the brushes:

http://www3.telus.net/martik/motor.jpg

"Martik" wrote in message
news:Hj3Id.133368$KO5.1002@clgrps13...

"James Sweet" wrote in message
news:zy%Hd.13338$Os6.4292@trnddc08...

"Martik" wrote in message
news:jeIHd.36644$06.34415@clgrps12...
Posted here a while ago broken speed control: Well they sent me a
new
one - no charge! but the damn thing still won't work. The motor just
hums
in
all positions of the control. I measured 100VDC going to 2 of the 4
wires
to
the motor. The motor bearings and brushes look good. Any ideas what
further
diagnosis I could pursue?



There's 4 wires to the motor? I had assumed the brushes would be in
series
with the field coil, you need voltage to both pairs of wires for the
motor
to run.

The 2 wires to the brushes have the 100VDC, I do not know what the others
are for.

Here is a picture, the red and blue wires go to the brushes:

http://www3.telus.net/martik/motor.jpg



Can't really see much there, that's definitly the commutator of a universal
motor though. As I said before, you need power to the stator windings for
the motor to run, otherwise you'll just burn up the armature.

On Fri, 21 Jan 2005 08:46:31 GMT "Martik" wrote:


"James Sweet" wrote in message
news:zy%Hd.13338$Os6.4292@trnddc08...

The 2 wires to the brushes have the 100VDC, I do not know what the others
are for.

Here is a picture, the red and blue wires go to the brushes:

http://www3.telus.net/martik/motor.jpg

While most small DC motors that I'm familiar with these days have
permanent magnet stators, 2 extra wires imply that there must be a
stator field coil. Your photo is very good, but it's too close up to
see the whole motor and how it's built.

I suspect, however, that it has field windings which are not getting
any power. It needs voltage across BOTH the brushes AND the field
windings.

-
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Jim Adney
Madison, WI 53711 USA
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