Steve Weeks writes:

On Wednesday, February 13, 2019 at 3:49:50 PM UTC-6, Tanguy Ortolo wrote:
Well in fact, I will not need to try with another wheel. As I was riding
home, the noise kept increasing, and at some point, my front wheel
started to slow me with a drag similar to slightly pulling on the
brakes.

That's how my first dynohub failure presented itself. With the wheel
off the ground, it wouldn't even spin a full revolution because of the
friction in the bearings. If you look at the link I posted before, you
will see a step-by-step account of the repair of a dynohub. It may be
that the hub I repaired is similar enough to yours that you can figure
it out. The "Joule I" hub and the Shimano hub may both be made by
Sanyo, in which case some similarity is likely. The Joule I hub has
two sealed cartridge bearings; the Shimano hub looks like it has one
cartridge bearing on the output side and a cup-and-cone bearing on the
non-output side.
You will need soldering equipment, but I doubt there is any aluminum wire to deal with.
If you are careful, you may be able to expose the solder joint by
carefully prying the superficial parts off (see the link!). I
initially did not do this, and broke the output wire and had to splice
it (also described in the link).
Good luck!

Almost all of this is unfounded speculation.

I have serviced my Shimano dynamo hub. I did break the wire. After
repair, it has worked perfectly for years afterwards.

The Shimano hub is made by ... Shimano. It has two loose ball bearings,
no cartridge bearings. The windings *are* aluminum, and it is easy to
break the wire lead when disassembling the hub. Unless you are careful,
you will need flux and solder for *aluminum* wire. If you break the
lead, solder a braided copper pigtail onto the aluminum wire, and you're
golden.

There are several pictorial guides to Shimano hub service on the web,
eg http://www.fahr-rad-os.de/tek/docs/dh-3n71_warten.pdf .



--