How to Bypass VS Switch

I have this Dremel tool (made by a Canadian Co.) about 15 years old and the VS switch is gone (works only at very low speed). I was thinking if there is way to bypass the VS switch and connect the power straight to the motor and then use a router speed control I have (shown on last picture) to control the speed.

The pictures shows the motor with the VS module plugged at the end. This module has 4 pins plugging into the motor and I have identified each pin for help. My problem is that I can see the B terminal (which the Black wire connects into) also connect to one end of the VS switch but I can’t see where the other end of the switch connects.

Is it possible to remove the VS switch?

Hi,
that looks like a series wound universal motor.

Can you measure the resistance of A-D and B-C. I suspect these are the two field windings and would expect them to 10 Ohms each or less,
so you'll need a good multimeter or other low resistance measuring device like a Kelvin bridge.

If it is indeed a series wound universal motor then your idea should work.

Craig

Have you tried flushing the switch out with contact cleaner? If it's an old pot may just fix it.

Sent from my SM-N970F using Tapatalk

Quote:

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Originally Posted by joeavaerage

Hi,
that looks like a series wound universal motor.

Can you measure the resistance of A-D and B-C. I suspect these are the two field windings and would expect them to 10 Ohms each or less,
so you'll need a good multimeter or other low resistance measuring device like a Kelvin bridge.

If it is indeed a series wound universal motor then your idea should work.

Craig

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Between A & D or B & C I get nothing but between A & B I get 12.5 Ohms and between D & C I get 10.2 Ohms

Thanks

Quote:

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Originally Posted by boydage

Have you tried flushing the switch out with contact cleaner? If it's an old pot may just fix it.

Sent from my SM-N970F using Tapatalk

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The switch has 3 contacts which they slide on 3 metal strips, one of the contacts is broken so no cleaning will fix this

Thanks

Hi,
on the basis of those measurements I would guess you have a series wound universal motor, although not the wiring I
expected. Give me a while to think about it.

Craig

Before I decided to remove the VS switch I bought a similar switch from Amazon and although the 4 pins were a bit off I managed to install it and it worked. However when I remove it to double check everything, the connection where the Black wire was attached broke off and then I decided to scrap this switch.

However this morning looking at it again I “think” I found where it broke off and I re solder the connection. Since I don’t want to damage the motor is there any way to test the 4 pin module before I plug it to AC to assure what I did is correct?

Hi,
to test run try a lower input voltage, ideally a Variac turned down to 50VAC say. Alternately feed it through a 100-200W incandesant light bulb.

Craig