Defective Dremel multi-tool clone (Tolimor Compact Tool MB130) - Page 1
Forum section: electronics / repair

author: Greybeard
author_rank: Frequent Contributor
timestamp: March 11, 2025, 11:20:34 pm
content: Hello,I have a Dremel multi-tool clone (Tolimor Compact Tool MB130) that has hardly been used and no longer works. I measured it with an ohmmeter, the rotor windings have no continuity on the opposite commutator segments, i.e. exactly where the carbon brushes are normally located. I measured all positions, no continuity.I wonder how that is possible, the winding looks completely intact. There is also no discoloration that would indicate overheating. The commutator and the brushes are almost as good as new and not worn in. I could imagine that one of the windings on the rotor has burned out or broken wire, but all at the same time, that is rather unlikely.What do you think?I haven't found a picture of the device, but apart from the color of the housing (the Tolimor is grey) and the different manufacturer labels, it looks exactly like the attached picture:

author: thm_w
author_rank: Super Contributor
timestamp: March 11, 2025, 11:27:12 pm
content: Can you return it under warranty?Can you trace the wire connection to the commutator? To check that it is at least connected in that area.

author: Greybeard
author_rank: Frequent Contributor
timestamp: March 12, 2025, 12:17:25 am
content: No longer under warranty - it's 5 or 6 years old.I've traced all the connections (wires), and everything is fine, except for the rotor windings themselves.

author: onesystem
author_rank: Regular Contributor
timestamp: March 12, 2025, 12:28:00 am
content: Try polishing commutator with paper or a papertowel, if you have some kind of polishing paste - use that. Do it a lot, then retest. Sometimes although looking clean, they get a film of sort that makes them insulated.

author: Greybeard
author_rank: Frequent Contributor
timestamp: March 12, 2025, 12:45:16 am
content: I've already cleaned it with fine steel wool.Bare copper, like new.But still no continuity.

author: onesystem
author_rank: Regular Contributor
timestamp: March 12, 2025, 12:50:37 am
content: Ok. This certainly seems strange. How could all of them burn out at the same time or disconnect even. Can you post pictures of the rotor and commutator?

author: Greybeard
author_rank: Frequent Contributor
timestamp: March 12, 2025, 12:54:15 am
content: Quote from: onesystem on March 12, 2025, 12:50:37 amNot now, here in Germany its's 2 o'clock in the night.Maybe tomorrow. I go to bed now, I'm really tired...

author: factory
author_rank: Super Contributor
timestamp: March 12, 2025, 02:20:03 pm
content: Quote from: onesystem on March 12, 2025, 12:28:00 amCleaning the commutator patina will reduces the life of the brushes (not that it probably matters in a disposable tool) and also removes the evidence of the possible cause of the problem (if there was one), lots of PDFs with info on problems with motors here;https://www.morganperformancecarbon.com/en-gb/resources/technical-data-and-support/rotating-machines/I've repaired another one of these generic rotary tools (branded Guild), there were two problems, first the design of the brush-holders & brushes, the brush wire gets twisted up & can break off when unscrewing/screwing the cap, some older Dremel brushes seem to be designed with just a spring to eliminate this issue.Second was the cause of the failure, the choke on the PCB was open circuit on one side, right where some hot melt glue was, replacing this got the tool working again.Note the design of the casing is a bit crap, the bearings & field are held in place by the two plastic halves, it took a few attempts to get it screwed back together without being to stiff to easily turn, I do wonder if this contributed to the choke failure, through being to stiff & having excess current draw.I'm sure there was a slight offset to the brush-holder positioning on this one, i.e. they weren't exactly opposite, maybe yours is different.David

author: Greybeard
author_rank: Frequent Contributor
timestamp: March 12, 2025, 09:01:55 pm
content: Quote from: factory on March 12, 2025, 02:20:03 pmThanks, very interesting in principle, but my problem is definitely the rotor windings.I measured the 0° and 180° positions on the commutator, all sectors, pressing the probes directly onto the commutator.Uncleaned and cleaned probes made no difference.Sorry for not posting any photos; I had already screwed everything back together and didn't have time because there's a water pipe burst in my apartment at the moment.

author: Analog Kid
author_rank: Super Contributor
timestamp: March 13, 2025, 02:37:47 am
content: You've obviously got a burned/otherwise no longer connected wire in the armature.Time to shitcan it and move on. No repair possible, unless you're contemplating rewinding the whole damn thing.What do you want for what you paid for it?

author: Greybeard
author_rank: Frequent Contributor
timestamp: March 13, 2025, 07:06:50 pm
content: I don't want to repair the winding since I can buy a new one for $30.I was just wondering how all the rotor windings could fail.

author: Analog Kid
author_rank: Super Contributor
timestamp: March 13, 2025, 07:33:34 pm
content: When you measured continuity, are you sure you tried all the possible contact positions? You might have been "off by one" even though you thought you were measuring the two contacts 180° apart. Sometimes hard to tell, as there are a lot of contacts on those commutators.