how to bypass dremel tool internal variable speed control?

The Guy I work with had the same experience as you. His second Dremel Oscillating tool quit. He thought the problem was the speed control.

I bypassed the speed control today. Also I bypassed the switch.

Holding the tool with the switch/speed control up (tool unplugged) and the access panel off snip the black and white wires (where the power comes to the speed control) up as close as possible to the speed control. The leads are short.

Next with the tool still in this position you will see a wire coming from the left side. It goes under the carbon brush assembly on the left and comes to the speed control. This wire will pull out of a little tab (where it plugs in to a slot in the top left corner of the opening you have with the access panel off). I think this is supposed to be the power coming back from the switch. I pulled this out and discarded it. It was corroded and loose in the slot. Possibly this was the actual problem. I was too far to turn back.

Now with the tool still pointed away and access opening up - notice there are two wires coming from the right side to the speed control. If the power is hooked to these two wires the tool will run (unless there's another problem).

So, I bought a 10 amp toggle switch 4.95 at the hardware store. I drilled a hole in the left side of the access panel and hooked up the switch to power up the two wires mentioned above. I soldered insulated stranded wires on to the toggle switch connections and made all the other connections with very small scotchlocks (with cone shaped springs inside).

It will work until it stops.

The problem with the tool seems to be the "tab" - "slot" connections. With all the vibrating and dust they probably end up arcing. That wasn't thought out well.

What symptoms?

No, of course that won't work! What it has, is an SCR/triac light-dimmer type phase control circuit, followed up by a bridge rectifier into the DC motor. So, you'd want to ignore the potentiometer entirely, and wire from the SCR/triac MT1 terminal to the MT2 terminal.

But, those hardly ever go bad; have you cleaned and checked out the brushes, which DO wear and become intermittent, and have you inspected the commutator?

I had to replace the variable assembly on mine a few years ago. comes as one assembly including pot and semiconductors. I ran the one I owned before that on a variac to control the speed. Mikek

Why are we paying attention to a post that's over 7 years old?

I don't know, I responded to the one at 3:11pm. It does interest me how these are revived, I don't see the OP on my reader. How did it get attention again? Mikek

Google Groups, AFAIK.

Sometimes the resurrected threads are interesting. Not this one so much.

Cheers

Phil Hobbs

Oddly enough, I don't complain when an interesting thread is resurrected.

Gee, that is odd. ;)

Cheers

Phil Hobbs

Details details!

Jamie

-190psi ...They have a much diffrent sound at those pressures and the neighbors will all be over finding out jusy what the hell all that screaming is about. I usually run my high speed cutoffs and such that high but get good wheels because them Chinese garbage discs will wear out quick as all heck and they tend to fly apart at wellheck any speed so save yourself a trip to the ER and at least use good abrasives. Now party on fellers and lets also get them 7