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bad switch on dremel multipro 395 type 5 variable speed Answered

im told the switch for the tool is obsolete, there isnt a serial # on the warning lable or any where else on tool only these #'s pa6-gf33, lr5947 and near cord in circles 7  6  8. i dont know witch switch to use. thanks for any help!.

2 Replies

Jack A Lopez (author)2015-06-28

A Google(r) image search for the words "dremel speed control circuit"


returns a bunch of circuit diagrams, and also pictures upped by people who took their Dremel(r) tools apart. That search was how I found,


but there might be other useful clues to be found in the original search results. I haven't looked through all of them.

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Jack A Lopez (author)2015-06-28

I am guessing the, what you call a "switch", is actually a potentiometer ( a variable resistor) and a triac based power control circuit.

Well, actually, it is less guesswork than you think, because this page,


has some pictures of a Dremel(r), in various stages of disassembled-ness, including a picture of the circuit board that does the power throttling.

If you are skilled at soldering tiny, tiny things, you might be able to rebuild your Dremel tool's power throttling circuit.

Another possibility is to just rewire the Dremel without the switch (i.e. with the motor connected directly across hot and neutral), and then use a dimmer-switch-in-a-box to facilitate the power throttling, erm whatchallit? Maybe "speed control" would be the approximate words for it.

There exist ibles here, for example,




show how to build a box with a lamp dimmer in it.

Also I claim the Dremel's original power throttling circuit is something similar to a lamp dimmer. It is essentially a triac that magically gets turned on for some fraction of the time of the period of the AC waveform, according to the position of the potentiometer knob or slider.


So throttling power to your Dremel tool by way of a lamp dimmer is not such a crazy far-out idea. Although I admit it might not look as pretty as the original "speed control" lever thingy, erm I guess you call it a "switch", on the tool itself.

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