Is it possible to simply swap out an old incandescent front light with any sort of halogen light, or are there specific "compatibility requirements" for the dynamo and rear light used?

My setup consists of:

• A Union model 4290 incandescent front light which was just KO'ed and needs replacing*
• A 2-month-old Busch & Müller 339AS incandescent rear light*
• An old Soubitez 6v/3w bottle dynamo which (usually) manages to light the two lights above fine**

Since the front light is dead, I saw that the price of a cheap halogen light needn't be much more than that of a cheap incandescent. Could I simply just attach one, or does it need more power/different resistance/etc.?

* Interesting that the website has a little flag apparently for an English translation... which happens to to do nothing. Anyway, there's nothing special about these cheap lights: I simply wanted to link to an image of them.
** While browsing teh Internets, I just noticed that these dynamos are being sold for a ridiculous amount of money... So it seems my next question is now: How do you refurbish old bottle dynamos?

Halogen bulbs are incandescent bulbs, just with a different fill gas.

The dynamo lights are meant to be interchangeable. The front lights take 6V/2.5W and rear 6V/0.5W or less. Halogen is only used for front. There is only one subtlety regarding halogen in that they are less tolerant to overloading than standard incandescent. A good halogen will have a protection built in, but cheap might not. If you ride a cheap front halogen off a standard 3W dynamo and do not connect a rear lamp or connect an LED rear lamp, you may blow the front when at high speed.

Thanks; It seems that also on some sites there is mention of simply replacing the "normal" incandescent bulb with a "halogen" one... is this really possible?? (Halogen functioning at a higher temperature and such) I have a spare "normal" incandescent light which I could install if that's the case.

Also, I found on the internet pictures of my old front light from about 7 months ago which I threw out because it didn't work. Turned out that was a Soubitez straight out of the '70s too. 'Doh. How often do these things turn up for sale online, anyway?

The filament in the halogen bulbs is oriented differently than in the standard incandescent. The optics is optimized differently depending on the orientation. If you replace one bulb with the other you will notice a significant increase in the brightness, but typically at the cost of an erratic pattern of illumination. For the replacement, be careful to get the correct screw-in base.

If the light is really a goner, get an LED replacement. For a decent cheapish light I'd go with a B&M Lumotec Lyt. In the US, available from Peter White: https://www.peterwhitecycles.com/b&m-hl.asp

Yeah, I was going to say the same thing - I checked the date on the post to make sure it wasn't a reopened thread from 5 or more years ago. With the Lyt, for only $50 you can get a WAY brighter light an LED than you can get with any sort of incandescent or halogen bulb.

There should not be anything inside a Soubitez generator but copper wire coils, magnets, iron, and a bearing. If it moves dodgy, the bearing needs cleaning. Carefully look at all the screws and see if you can take the little beastie apart. I would not mess with the pivot and latch without a good reason - springs inside! If you can do all this without disturbing the magnets, do that. If the magnets are on the rotating shaft (I guess they have to be, actually!), don't chip them.

Clean the bearing areas with rags with a dab of solvent on them - focus on elbow grease rather than solvents, due to the age of the wire insulation, about 40 years.

To reassemble, what to lube with? I'm not an oils expert, but I'd try a drop of 3 in 1 Electric Motor Oil, or maybe just a drop of automotive motor oil, just 10w-40 or something common. Not a lot, because if it's a wrong choice you don't want gunk to build up.

When you turn the roller by hand you should feel distinct steps in the rotation (caused by the magnetics) but smooth motion without binding, end play or radial play.

There is the screw base change to flange base too

I have some older Union Halogen headlight units . FS..

Unfortunately I was already stupid enough to take the spring out-- after about 5 hours I got it back in and it worked (even though it didn't "feel" the same afterwards). As to its current state, it definitely still "clicks" a bit when you turn it, and the turning doesn't feel "rough" either. This is why I'm even more confused about how to fix it... For example, when I push the dynamo a bit with my foot so it rubs "harder" on the tire, it lights fine. Even more stranger is that occasionally when riding I will feel it "kick in" and get more traction, adding friction to the ride but also lighting correctly... do I just need to somehow get it to "spring" closer to the tire? I really doubt it, but...