Wiring an electric drill

[David Nebenzahl]

I feel a little ashamed asking this question here, as it isn't really a
proper electronics question, but not finding any better place to ask it,
here goes. I'm trying to revive my trusty old electric drill (Craftsman
3/8" variable-speed reversible, all metal, not plastic, thank you very
much). Years ago the speed control crapped out, and I ordered a
replacement from Sears. When I put the new one in, the drill worked, but
not very well: a lot of sparking from the brushes and erratic operation,
like stalling and having to spin the shaft to get it running again.

So far as I can tell there's nothing mechanically wrong with it. Like a
lot of things from the past, it's built like the proverbial brick
shithouse. I cleaned the commutator; the brushes are solid and clean,
bearings well-lubed and free-spinning.

I think I just screwed up wiring the damn thing together. I have no
diagram, and followed what I *thought* was the way it was originally,
but apparently I've done something stupid.

The way it's wired now puts the field and commutator in series, which I
believe is correct for this type of universal motor. I tried reversing
one set of connections, but that didn't help, or even seem to make much
difference at all.

Does anyone know how these things get wired? Anyone have a wiring
diagram for this, or similar, drill?

Any help appreciated.


--
Pierre, mon ami. Jetez vous une plus de Scientologiste
dans le vat de l'acide.

- from a posting in alt.religion.scientology titled
"France recommends dissolving Scientologists"

 

[n cook]

I feel a little ashamed asking this question here, as it isn't really a
proper electronics question, but not finding any better place to ask it,
here goes. I'm trying to revive my trusty old electric drill (Craftsman
3/8" variable-speed reversible, all metal, not plastic, thank you very
much). Years ago the speed control crapped out, and I ordered a
replacement from Sears. When I put the new one in, the drill worked, but
not very well: a lot of sparking from the brushes and erratic operation,
like stalling and having to spin the shaft to get it running again.

So far as I can tell there's nothing mechanically wrong with it. Like a
lot of things from the past, it's built like the proverbial brick
shithouse. I cleaned the commutator; the brushes are solid and clean,
bearings well-lubed and free-spinning.

I think I just screwed up wiring the damn thing together. I have no
diagram, and followed what I *thought* was the way it was originally,
but apparently I've done something stupid.

The way it's wired now puts the field and commutator in series, which I
believe is correct for this type of universal motor. I tried reversing
one set of connections, but that didn't help, or even seem to make much
difference at all.

Does anyone know how these things get wired? Anyone have a wiring
diagram for this, or similar, drill?

Any help appreciated.


--
Pierre, mon ami. Jetez vous une plus de Scientologiste
dans le vat de l'acide.

- from a posting in alt.religion.scientology titled
"France recommends dissolving Scientologists"

Probably some shorted turns on part of the armature windings -> excess
current -> exceeded current handling of speed regulator -> knocked out speed
regulator -> repeating the same route to destrucyion.

 

[David Nebenzahl]

n cook spake thus:

Probably some shorted turns on part of the armature windings -> excess
current -> exceeded current handling of speed regulator -> knocked out speed
regulator -> repeating the same route to destrucyion.

Close. Not shorted but open windings: one of the commutator bars worked
loose and both wires that attached to it were disconnected. I managed to
solder them back on, and gave the whole assembly a nice bath in CA
(superglue), since there were cracks all the way around where the bars
attach. Waiting for everything to dry before trying it, but I have high
hopes that it will spin smoothly again.


--
Pierre, mon ami. Jetez vous une plus de Scientologiste
dans le vat de l'acide.

- from a posting in alt.religion.scientology titled
"France recommends dissolving Scientologists"

 

[Neil J. Harris]

Since you have it in bits anyway can you get it to run from low voltage
dc sources with separate field and armature supplies?
You might have an open winding on the armature, or shorted turns. This
would give lots of sparking (and destroy you new controller).