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30 October 2018
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Dremel 3000 Faulty Stator

The Dremel 3000 is a big investment for most people, especially when you take into account, all the accessories that you'll probably end up buying along with it, so when ours suddenly stopped working, we weren't too impressed.

Dremel-3000-Features


We'd used it only a few times, did some PCB drilling using the workstation stand, bits of sanding and grinding, and some polishing using the flexible extension shaft. All in all, it was great, and now that it stopped working, our world sank.

So, the decision was taken to open it up and have a look inside. You'll need to slice through centre of the labels either side of the tool with a sharp utility knife, otherwise you won't be able to get the two halves of the casing apart.

Dremel 3000 Exploded View


What we found was that a wire from one of the stator coils had broken away from the metal connection lug. On further inspection, the metal lug design is somewhat poor, where it forces the wire inside, effectively pinching it to establish a good contact, but weakening it at the same time.

The solution was actually very simple. Instead of having to buy a replacement field coil (stator) for around £20, a simple solder job with a couple of copper wire strands from some scrap wire was all that was needed. Having stripped the wire to expose the copper strands, we tinned two of the strands together, and then soldered them to the existing wire. Just a note for anyone trying this: you need to scrape away some of the clear enamel lacquer to expose the copper, otherwise the solder won't bond and it seems that a 300ºC soldering iron tip was not hot enough to melt through it. You can do this by running the blade of a utility knife along the wire to scrape the enamel away.

 Dremel 3000 Soldering Broken Coil Wire


We added a small amount of heat shrink just as a precautionary measure just in case our newly exposed wire somehow shorted through the lacquer of the rest of the coil, and simply tucked it out of harm’s way. The pair of wires were then fed under the metal connection tab, which was pushed back into place after initial removal with a pair of narrow pliers.

Just to double check that the solder job was up to spec, the 2 coils within the stator were checked for resistance, and they measured up exactly the same - About 25 ohms in our case.

Checking coil resistance with a multimeter


Reassembly was the opposite of disassembly, noting which screws went where (there were 2 types of screws, one for the case, and the other for the strain relief clamp). The case sections at the sides around where the carbon brushes were a little fiddly to manoeuvre into place, but nothing had to be forced.

Dremel 3000 Reassembly


One final thing to note was that the bearing nearest the cable had a rubber sleeve over it (no doubt to dampen vibration). This slipped off quite easily, assisting the removal of the rotor from the inside of the stator, and could be easily slipped back on again when the rotor was reinserted.

Putting everything back, it all worked, but we noticed that the running was very rough, and that lower speeds would splutter if not cut out. A quick check of the carbon brushes revealed that they were not put back exactly the same way they were taken out (the wear seems uneven), so the contact was different while they were reseating. Fortunately, we did have a spare pair of brushes, and when they were inserted, it seemed as good as new. The old carbon brushes may be reused, but they'll be given a concave profile first to help seat them.

So, fingers crossed, the drill will battle on for the time being, but it did make us go out and buy a cheap pneumatic micro die-grinder. Even though we have an air supply, the die grinder doesn't feature an accessory thread which makes Dremel so versatile. This is something we hope to fix with a custom-made adaptor soon.

External Links:

Dremel UK Website: https://www.dremeleurope.com/gb/en/
Dremel Facebook Page: https://www.facebook.com/UKDremel/

If this repair was helpful, please let Dremel know! ;-)

Comments:

  • Same fault, different stator coil!
    Brent Stevens - August 8, 2017, 11:20 am
    It happened again! Just a week later, the drill just died. Opened it up and exactly the same fault. A wire on the opposite stator coil had failed in the same place as the first. Fortunately, we were able to make a quick repair and get it up and running in next to no time!

    Dremmel, your drills are great, but this is a design flaw and should be improved on a design update.
  • Faulty dremel
    Gentry - September 16, 2017, 1:31 pm
    Great tutorial. My dremel also died just being a short time out of warranty. Opened up and there was no continuity between one coil.

    I tried to solder it and now there is a connection. But resistance differs a butt. One has 24.4 Ohm the other (repaired) one has 24.0 Ohm. Does this make a difference because it is still not working.

    I have a suspicion that the switch is broken. The dremel died during use and I may have covered air inlet. It turned off but then only touching the carbon brushes from outside it came back on. Then died for good. Brushes seem to be fine as far as I can tell.

    Maybe the triac died but I don't know how to check.

    Any ideas?
  • RE: Faulty dremel
    Brent Stevens - October 5, 2017, 1:30 am
    The difference between the two coils isn't that large.

    I noticed that when I first reassembled the carbon brushes it ran very rough and started to cut out, quite like you're describing. Mine had spare brushes, so used then instead, and it instantly ran smoother, and got progressively better if I ran it at high speed.

    It seems that when you put the carbon brushes back in (even if they don't have much wear on them), they're possibly not seated correctly, and therefore not making the correct contact onto the rotor.

    Sorry for the late reply, hope this may still help.

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