I'm on my second electronic variable speed control inside my Dremel
model 395 tool. This one just crapped out with the same temperamental
symptoms as the last one. I need to use the tool tomorrow night, and
would like to bypass the internal variable speed circuitry to simplify
it; maybe buy an external control later.

There aren't any wiring diagrams I could find on the Dremel site. I'm
thinking if I had one for the model 275 tool (single speed) and the
395 (electronic variable speed), I might be able to make the 395 into
a 275 by just jumpering some wires. I'll probaqbly need to at least
retain the variable speed assembly, since the brushes fit into it.

Can anyone help?

wrote:

I'm on my second electronic variable speed control inside my Dremel
model 395 tool. This one just crapped out with the same temperamental
symptoms as the last one. I need to use the tool tomorrow night, and
would like to bypass the internal variable speed circuitry to simplify
it; maybe buy an external control later.

There aren't any wiring diagrams I could find on the Dremel site. I'm
thinking if I had one for the model 275 tool (single speed) and the
395 (electronic variable speed), I might be able to make the 395 into
a 275 by just jumpering some wires. I'll probaqbly need to at least
retain the variable speed assembly, since the brushes fit into it.

Can anyone help?

Obvious, it's junk! Buy a new model dremel.
or better yet, by one of those no name brands
like I did, looks like it's made in the same place
but cost much less!
$29.00 for a complete set of cutters, stones with
variable speed unit.
I think it was "All Trade" or "TradeAll" or something like that.


--
"I'm never wrong, once i thought i was, but was mistaken"
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5

wrote:
I'm on my second electronic variable speed control inside my Dremel
model 395 tool. This one just crapped out with the same temperamental
symptoms as the last one. I need to use the tool tomorrow night, and
would like to bypass the internal variable speed circuitry to simplify
it; maybe buy an external control later.

There aren't any wiring diagrams I could find on the Dremel site. I'm
thinking if I had one for the model 275 tool (single speed) and the
395 (electronic variable speed), I might be able to make the 395 into
a 275 by just jumpering some wires. I'll probaqbly need to at least
retain the variable speed assembly, since the brushes fit into it.

Can anyone help?



Hi

Just take it apart, I'm pretty sure it's just a "potentiometer"
(variable resistor) so it would only have 3 leads, one from the external
wire to the pot., one from the pot to the motor, and one from the other
external wire to the other lead of the motor.

Cut things off, plug the external leads directly to the motor.

You can make yourself something that would do the same with a variable
light controller (those you have to control your house lights) Get one
of these, one wall plug unit and one extension cord.

PWR IN (1) to VARIABLE (1)
VARIABLE (2) to PWR OUT (1)
PWR IN (2) to PWR OUT (2)

it would be an awesome idea to tape everything together to cover the
connections once you're done so you don't get shocked everytime you want
to slow it down or speed it up

Have fun


(PS I also have one of the new Dremel units and it smokes too ... Uh.)

Just take it apart, I'm pretty sure it's just a "potentiometer"
(variable resistor) so it would only have 3 leads, one from the external
wire to the pot., one from the pot to the motor, and one from the other
external wire to the other lead of the motor.

Cut things off, plug the external leads directly to the motor.



Unfortuantely it doesn't seem that simple. The speed control has what
looks like a some kind of semiconductor/IC (3 leads), a diode, and
maybe a fixed resistor in addition to the slide pot. I don't know if
they're doing pulse width modulation or what.

wrote:
Just take it apart, I'm pretty sure it's just a "potentiometer"
(variable resistor) so it would only have 3 leads, one from the external
wire to the pot., one from the pot to the motor, and one from the other
external wire to the other lead of the motor.

Cut things off, plug the external leads directly to the motor.


Unfortuantely it doesn't seem that simple. The speed control has what
looks like a some kind of semiconductor/IC (3 leads), a diode, and
maybe a fixed resistor in addition to the slide pot. I don't know if
they're doing pulse width modulation or what.



I doubt they have put a stepper motor in there, they wouldn't sell for
20$ each! -- You still should only have two leads coming out of the
motor. Confirm?

Claude Desjardins wrote:
wrote:
Just take it apart, I'm pretty sure it's just a "potentiometer"
(variable resistor) so it would only have 3 leads, one from the external
wire to the pot., one from the pot to the motor, and one from the other
external wire to the other lead of the motor.

Cut things off, plug the external leads directly to the motor.


Unfortuantely it doesn't seem that simple. The speed control has what
looks like a some kind of semiconductor/IC (3 leads), a diode, and
maybe a fixed resistor in addition to the slide pot. I don't know if
they're doing pulse width modulation or what.



I doubt they have put a stepper motor in there, they wouldn't sell for
20$ each! -- You still should only have two leads coming out of the
motor. Confirm?


Btw you said there was a IC ... how many pins does it has, can u give
out the ID (in case it's a bridge or something so your motor would be DC
(Uhm?!) and wouldnt be a great idea to plug it right into a wall outlet!

Claude Desjardins wrote:

wrote:
Just take it apart, I'm pretty sure it's just a "potentiometer"
(variable resistor) so it would only have 3 leads, one from the external
wire to the pot., one from the pot to the motor, and one from the other
external wire to the other lead of the motor.

Cut things off, plug the external leads directly to the motor.


Unfortuantely it doesn't seem that simple. The speed control has what
looks like a some kind of semiconductor/IC (3 leads), a diode, and
maybe a fixed resistor in addition to the slide pot. I don't know if
they're doing pulse width modulation or what.


I doubt they have put a stepper motor in there, they wouldn't sell for
20$ each! -- You still should only have two leads coming out of the
motor. Confirm?


Every Dremel tool I've had apart used a universal motor, and the
speed control was a simple dimmer circuit. This one might be PWM, and
run the motor on DC.

--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida

Michael A. Terrell wrote:

Claude Desjardins wrote:

wrote:

Just take it apart, I'm pretty sure it's just a "potentiometer"
(variable resistor) so it would only have 3 leads, one from the external
wire to the pot., one from the pot to the motor, and one from the other
external wire to the other lead of the motor.

Cut things off, plug the external leads directly to the motor.


Unfortuantely it doesn't seem that simple. The speed control has what
looks like a some kind of semiconductor/IC (3 leads), a diode, and
maybe a fixed resistor in addition to the slide pot. I don't know if
they're doing pulse width modulation or what.


I doubt they have put a stepper motor in there, they wouldn't sell for
20$ each! -- You still should only have two leads coming out of the
motor. Confirm?



Every Dremel tool I've had apart used a universal motor, and the
speed control was a simple dimmer circuit. This one might be PWM, and
run the motor on DC.

Most of the cordless drills these days use PWM power FeT drivers.

I modified a cordless drill with a mini PIC and Bridge to
perform regulated torque control, auto reverse and then forward
again until maximum torque was no longer peaking. Did this so that
the drill would have a TAP mode in it. I stuck a mini pot on the back
side of the handle to set the torque level.

if his dremel is also cordless, It may also be using it a PWM?
who knows. how ever, with the part count, I'm guessing he's using a
corded unit with a phase control.


--
"I'm never wrong, once i thought i was, but was mistaken"
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5

wrote in message
ups.com...
Just take it apart, I'm pretty sure it's just a "potentiometer"
(variable resistor) so it would only have 3 leads, one from the external
wire to the pot., one from the pot to the motor, and one from the other
external wire to the other lead of the motor.

Cut things off, plug the external leads directly to the motor.



Unfortuantely it doesn't seem that simple. The speed control has what
looks like a some kind of semiconductor/IC (3 leads), a diode, and
maybe a fixed resistor in addition to the slide pot. I don't know if
they're doing pulse width modulation or what.


Of course it's not gonna be a pot, it would have to be far too big and burn
up a lot of power. Instead they use what is essentially a light dimmer. The
semiconductor you see is a triac, the diode is a diac to trigger it, if you
just jumper together the right two pins on the triac, the motor will be
forced on.

"James Sweet" wrote in message
news:UI3Fi.1085$rw3.1000@trndny04...

wrote in message
ups.com...
Just take it apart, I'm pretty sure it's just a "potentiometer"
(variable resistor) so it would only have 3 leads, one from the external
wire to the pot., one from the pot to the motor, and one from the other
external wire to the other lead of the motor.

Cut things off, plug the external leads directly to the motor.



Unfortuantely it doesn't seem that simple. The speed control has what
looks like a some kind of semiconductor/IC (3 leads), a diode, and
maybe a fixed resistor in addition to the slide pot. I don't know if
they're doing pulse width modulation or what.


Of course it's not gonna be a pot, it would have to be far too big and
burn up a lot of power. Instead they use what is essentially a light
dimmer. The semiconductor you see is a triac, the diode is a diac to
trigger it, if you just jumper together the right two pins on the triac,
the motor will be forced on.

Don' it just hurt to the core, James ... ? !!! ;~)

Arfa

wrote:
Just take it apart, I'm pretty sure it's just a "potentiometer"
(variable resistor) so it would only have 3 leads, one from the external
wire to the pot., one from the pot to the motor, and one from the other
external wire to the other lead of the motor.

Cut things off, plug the external leads directly to the motor.



Unfortuantely it doesn't seem that simple. The speed control has what
looks like a some kind of semiconductor/IC (3 leads), a diode, and
maybe a fixed resistor in addition to the slide pot. I don't know if
they're doing pulse width modulation or what.

That's a simple phase control SCR circuit.
the diode is a DIAC.. etc..
if it's not firing, I would check the pot and
resistor.


--
"I'm never wrong, once i thought i was, but was mistaken"
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5

On Sep 10, 11:55 am, Jamie
t wrote:
wrote:
Unfortuantely it doesn't seem that simple. The speed control has what
looks like a some kind of semiconductor/IC (3 leads), a diode, and
maybe a fixed resistor in addition to the slide pot. I don't know if
they're doing pulse width modulation or what.

That's a simple phase control SCR circuit.
the diode is a DIAC.. etc..
if it's not firing, I would check the pot and
resistor.

Trace it with a volt meter. Probably a bad solder job and the heat
from the controller loosened something up. Easy fix if you have a
decent iron.

wrote:
I'm on my second electronic variable speed control inside my Dremel
model 395 tool. This one just crapped out with the same temperamental
symptoms as the last one. I need to use the tool tomorrow night, and
would like to bypass the internal variable speed circuitry to simplify
it; maybe buy an external control later.

There aren't any wiring diagrams I could find on the Dremel site. I'm
thinking if I had one for the model 275 tool (single speed) and the
395 (electronic variable speed), I might be able to make the 395 into
a 275 by just jumpering some wires. I'll probaqbly need to at least
retain the variable speed assembly, since the brushes fit into it.

Can anyone help?


I'm not positive, but I would think if you just soldered a wire around
the speed control it would run at full speed, I could be wrong though.

-Landon

wrote:
I'm on my second electronic variable speed control inside my Dremel
model 395 tool. This one just crapped out with the same temperamental
symptoms as the last one. I need to use the tool tomorrow night, and
would like to bypass the internal variable speed circuitry to simplify
it; maybe buy an external control later.

There aren't any wiring diagrams I could find on the Dremel site. I'm
thinking if I had one for the model 275 tool (single speed) and the
395 (electronic variable speed), I might be able to make the 395 into
a 275 by just jumpering some wires. I'll probaqbly need to at least
retain the variable speed assembly, since the brushes fit into it.

Can anyone help?


If you cannot figure that out by looking, you probably should not be
dicking around with it.

The last fried speed control in a chinese one I bought, took a buck's
worth of a new triac to fix.

Cheers
Trevor Jones

the speed control is a triac based phase control, the same as a light
dimmer - typically it has two wires, just short the two wires together and
the dremel will run full speed all the time.

by the way, typical failure is just noisy pot, try cleaning carbon track
wrote in message
oups.com...
I'm on my second electronic variable speed control inside my Dremel
model 395 tool. This one just crapped out with the same temperamental
symptoms as the last one. I need to use the tool tomorrow night, and
would like to bypass the internal variable speed circuitry to simplify
it; maybe buy an external control later.

There aren't any wiring diagrams I could find on the Dremel site. I'm
thinking if I had one for the model 275 tool (single speed) and the
395 (electronic variable speed), I might be able to make the 395 into
a 275 by just jumpering some wires. I'll probaqbly need to at least
retain the variable speed assembly, since the brushes fit into it.

Can anyone help?




--
Posted via a free Usenet account from http://www.teranews.com

William Noble wrote:
the speed control is a triac based phase control, the same as a light
dimmer - typically it has two wires, just short the two wires together and
the dremel will run full speed all the time.

by the way, typical failure is just noisy pot, try cleaning carbon track

Mine had a smd triac BT134W which was faulty.

I replaced it (easy!!) with a new one, and
the dremel has worked years after that. The
triac costs about 1 usd.. The parts are on a
white ceramic circuitboard.

Kristian Ukkonen.

hillpc wrote ...
I'm on my second electronic variable speed control inside my Dremel
model 395 tool. This one just crapped out with the same temperamental
symptoms as the last one. I need to use the tool tomorrow night, and
would like to bypass the internal variable speed circuitry to simplify
it; maybe buy an external control later.
. . .
Can anyone help?

This is one of those cases where "If you don't know already, you probably
shouldn't be doing the job".

The wiring should be simple enough to do it by inspection. If it isn't, you
really need the schematic and the ability to understand it.

Unlike the other poster, I really doubt that the motor speed control is just
a pot.


--
Bill Fuhrmann

Thanks, folks. This discussion is exactly the type of info I
needed.

after you make your temporary repair, dremel sells all the parts you might
need for a nominal cost if you call customer service.


wrote in message
ups.com...
Thanks, folks. This discussion is exactly the type of info I
needed.

On Sep 9, 9:21 pm, wrote:
I'm on my second electronic variable speed control inside myDremel
model 395 tool. This one just crapped out with the same temperamental
symptoms as the last one. I need to use the tool tomorrow night, and
would like to bypass the internal variable speed circuitry to simplify
it; maybe buy an external control later.

There aren't any wiring diagrams I could find on theDremelsite. I'm
thinking if I had one for the model 275 tool (single speed) and the
395 (electronic variable speed), I might be able to make the 395 into
a 275 by just jumpering some wires. I'll probaqbly need to at least
retain the variable speed assembly, since the brushes fit into it.

Can anyone help?

Not to dig up an old topic, but I just ran into this
http://mondo-technology.com/dremel.html

"Marc Britten" wrote in message
oups.com...
On Sep 9, 9:21 pm, wrote:
I'm on my second electronic variable speed control inside myDremel
model 395 tool. This one just crapped out with the same temperamental
symptoms as the last one. I need to use the tool tomorrow night, and
would like to bypass the internal variable speed circuitry to simplify
it; maybe buy an external control later.

There aren't any wiring diagrams I could find on theDremelsite. I'm
thinking if I had one for the model 275 tool (single speed) and the
395 (electronic variable speed), I might be able to make the 395 into
a 275 by just jumpering some wires. I'll probaqbly need to at least
retain the variable speed assembly, since the brushes fit into it.

If it runs at all, hopefully at full speed, jst plug it in to a sewing
machine rheostat, Works fine for me.

Boris

In the Dremel's I've taken apart there are few components because it's triac speed control (light dimmer).

probably close to this: https://www.electroschematics.com/mo...or-with-triac/

A jumper between the two terminals other than the one going to T2 is all you have to do.

if there is a number on the part. You jump MT1 to MT2.

e.g. https://www.nteinc.com/specs/5600to5...nte5621_27.pdf

All pin outs may not tbe the same.