Dremel 395 VSC repair

The components on my earlier model, for 240V ac use Dremmel Mod 358, ser 5-13, minidrill Triac BT24A, 100nF 250V, 10K,4.7K, 390K , 56R and log pot that measured 220K max, in cct

only switch is on/off, speed varied by pot

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

"N_Cook" wrote in news:h42376$vc6$ snipped-for-privacy@news.eternal- september.org:

I have a Dremel model 270(single speed),and I use an ordinary lamp dimmer as a speed control. I mounted it in a double outlet box with a duplex outlet that gives a variable outlet and a full 120VAC outlet. Then you can also use it as a soldering iron temp reducer.

I believe you'll find that the wide, black strip on the "board" is essentailly the same as the resistive element of a speed pot. It would be a resistive compound deposited directly onto the ceramic substrate.

The contacts on the button would seem to be acting as the wiper section of a speed pot, while also creating a path for one of the motor brushes.

If you are going to proceed with eliminating and substituting the original "board" speed pot, you would need to bypass the wide, black strip, in ase it is still condutive from one end to the other.

There are likely to be numerous examples of light duty triac circuits online, since many applications and products use this very basic circuit.

I've been using a foot speed control for a while now, and this method is very convenient and easy to get used to. Not only that, but the foot speed control is very versatile, as it has a power cord receptacle for plugging tools into, so it can be used for numerous small power tools. Other small AC/DC universal motors can/are conveniently used with it.

There are other products that would perform well as a method to vary speed (or temperature in the case of low-power heaters, soldering irons, for example).

One product is commonly referred to as a router variable speed control, which is functionally, essentially the same circuit as the Dremel varaible speed circuit, but rated for up to 15A (which is a lot higher than the Dremel's demand).

As for the foot speed control, I was kind-of expecting to see a circuit board when I opened the housing (as I usually always do), but the only part inside the sort-of unique housing is a trigger switch from a variable speed drill (rated for 6A). The Linemaster and Foredom units are just fancy boxes with drill trigger switches in them.

-- Cheers, WB .............

Hello:

Thank you so much for such a fast reply. Much appreciated. =-)

minidrill

max, in cct

Mine is also 220v, the one in the photo is 110v but identical in layout. I'll check and see about the similarities in components and have a try with a 220K log pot across the in/out of the board and measure the output voltage.

It would be good to be able to use the same circuit the thingie came with. Glue it on a small Al heatsink and put it inside an empty wall-wart with the AC cable going through.

I s.t.r. triac speed controls for motors that compensate for load torque, so the no-load speed holds fairly(?)(quite?) well under load.

There's a lamp dimmer made to be installed on ordinary "zip" lamp cord; it worked very well for me for years as a soldering iron power control, giving a great range of temperatures. I made a light-duty extension cord that used it.

These days, I'd worry about line spikes reaching the tip, capacitively coupled, although good modern ones probably have the shank connected to safety (earth) ground. Have no iron just now, but will get a soldering station when I spring for one.

Easiest way to control these is with a variac (variable autotransformer); somewhat costly, but it's a useful item for lots of other things, too.

Motor control rated 'dimmer' type devices are also available; the best are those intended for inductive loads, like 12V transformers driving halogen lighting (Lutron and other manufacturers make these in convenient wallswitch form). Incandescant-light dimmers are slightly different, and might work well or poorly.