Numatic NVD 750

[jonas]

One of the twin motors on my Numatic NVD 750 dust extractor has stopped working.
No smell of burning & no blown fuses
Any advice on how to proceed would be most welcome.

Its just out of guarantee. I wonder if Axminster will give me an extension for Covid    ?

Thanks in advance

Jonas

[Philip Green]

I have a record extractor that suddenly stopped working.

I diagnosed worn motor brushes, acquired new ones from Record, fitted them and all was well again.

Could yours be a brush issue? If so, suggest changing the brushes on both motors.

[Bill21]

Surprised to see you can get spare Numatic motor brushes on Amazon for not much money. Hopefully that’s the problem.

[jonas]

Thanks for the advise
I eventually got the thing apart and found (as suggested) one of the brushes was worn right down to the copper, but the other brush was hardly worn at all. Is it just a matter of fitting new brushes or is it likely that there is some other fault causing the one sided wear?

Unfortunately none of the brushes on Amazon are the correct type, but I think I have found some.

I see the price of a new Numatic from Axminster has gone up to £569. Thats nearly as much as I paid for my lathe.

Jonas

[Bill21]

I don’t know about the one sided wear but I’ve managed to bring life back to old machines by simply fitting new brushes. Once you can identify the part number for the replacement brushes hopefully sourcing them shouldn’t be a problem. Good luck.

[Bryan Milham]

If one brush is worn and the other not, I would suggest that the spring clip that holds the unworn won in place was not properly engaged, hence not supplying enough pressure onto the motor commutator.

[julcle]

As Brian says it will be a problem with the brush, it's probably sticking in the brush guide. it's a good idea when changing them to clean the brass guides out and just run the new brushes over a bit of sand paper so that they slide up and down smoothly with no restriction.
Best of luck --  Julian

[Wood spinner]

You could try a brush from the working motor to see if it runs OK the get some new brushes

[jonas]

Update.

I was very much mistaken when I said that only one brush had worn down. When I eventually got them out I found all 4 were almost down to the limit. I had been struggling to remove the old brushes when I realized that they came as a complete module, holder spring & brush, all preset. This made the replacement simple once I had found the modules on line, total cost £10.
 I have just had a quick run & it appears to be O.K. but time will tell.

The main reason for this update is to thank you chaps for your advice, but also to point out that the brushes in this machine do not have a long life. I have  had this machine for just over 3 years & am only a hobby turner. I would advise any one who has had one of these machines for a few years to check the brush gear, as worn out brushes can cause serious damage. I think I was lucky.

Just for reference, a new brush is 28mm long.

Jonas 

[Wood spinner]

Also even if you don't need brushes now it's good insurance to buy some spares NOW
I have been caught out several times and been told " Sorry no longer made " rendering a machine useless

The last one about to go for scrap is a miter saw 

[Bill21]

I have seen an advert in the past from a manufacturer that said they can make brushes for almost any machine.