I am in need of both a generator (dynamo) and a regulator. I took the cover off the regulator and the points are burnt to a crisp. Its not charging and im no electrical troubleshooter by any stretch.
I also noticed when running i can see sparks from around the armature. I have been wondering if new brushes could at least ring the generator ( dynamo) back online. 
As for the regulator its toast and needs replaced. Last question is does anyone here check and rebuild the generator (dynamo)?

Check brushes and battery.  Recommend locate and read all service manuals with similar charge system.  

you likely need to clean up the system vs replace it.  

 

I'm pretty sure I have a regulator or two lying around if you decide you need one.  As Pabdt said, they are fairly robust systems.  

By rebuild the generator (dynamo) is that just installing new brushes? I saw somewhere here a member sells brushes.

imgur.com/NtUMoTW
imgur.com/fHT7g3F
I do have a 3 or 4 page post that include the pictures on this site.
If my pictures come through you can see the differences of before and after. MY AT3 was not charging and all that I had to do was clean the commutator (the copper looking thing} with 400 or 600 grit sand paper and cleaned out the little separator lines with a sharp pick and razor blade. Mine then started charging. My brushes still had a tremendous amount of life left in them.

i.imgur.com/fHT7g3F.jpg
i.imgur.com/NtUMoTW.jpg