dyson motor repair

Hello,
I bought a second-hand Dyson dc04 from ebay from a chap who reconditioned them. So I have no way of knowing whether it had been used for 1 hour or 1001 hours before I bought it.
The underside of the base is a different colour to the rest of it suggesting it is a "cut and shut" and potentially has parts from more than one vacuum!
I had a phone call the other day to say that there was a burning smell coming from the vacuum. I have read here that Dysons are well known for overheating; especially if the filters get clogged.
When I got home I had a look. The filter was dirty but I didn't think it was that bad. I tried it and there was a bit of a burning smell.
I found some instructions on the internet of how to disassemble the vacuum. They were not a perfect match for my machine but good enough that I managed to dismantle it.
The motor itself looks pretty clean, though there was carbon inside the case. The problem is not knowing whether that's recent or whether it has been there for a long time.
The motor runs but it is illuminated with blue at the brushes. Does this mean that I need new brushes and can they be replaced or do I have to change the whole motor? OTOH some drills spark in normal use and they do not indicate a fault with the motor or its brushes. I'm thinking that with it being an unknown age, the brushes could have worn.
What else could cause the smell? I'm puzzled because I can't see anything that is obviously burned. Before I buy a new motor, I'd like to know what is wrong with the one I am throwing away. There is no obvious burnt area and it does not make any unusual noise in use. Can anyone satisfy my curiosity?
TIA Fred
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Fred wrote:

Check the brushes are free to slide in the guides and have reasonable pressure on the commutator. Provided that is the case then a small amount of sparking along the straight edges of the brushes is permissible but a ring of sparks from one brush perhaps extending to the other brush is indicative of a damaged armature and is beyond repair. The fault is usually an open circuit section of the winding or a shorted turn/s. This is the commonest fault on cheap/nasty universal motors used in domestic appliances.
Bob
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On 19/12/2011 20:45, Fred wrote:

Sounds obvious, but have you checked the belt on the brush roll?
--
David


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On 12/19/2011 5:22 PM, gremlin_95 wrote:

Good thought - that's what it always was, when my mother's vac produced a burning smell.
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wrote:

Thanks for all the help. I hadn't checked the belt. I'll have a closer look at that and the brushes after Christmas.
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Could the filter charged with stopping particles getting to the motor be clogged or the incorrect sort? Brian
--
Brian Gaff - snipped-for-privacy@blueyonder.co.uk
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