Are the contact surfaces plated? Its difficult to tell in the picture. If not the classic pencil eraser could remove any oxide and provide a fresh surface. It looks like the wipers are copper and the contacts are brass. Possibly a wipe with white vinegar/ acetic acid to remove oxide on the surface and then an thorough cleaning. when the oxides are strong the usual cleaners can't get through them. 10 milliOhm per step will be difficult to maintain accuracy since the switch would need microOhm contact resistance. That's really hard. Maybe silver on silver? That would be the classic Daven switch.
The color of the contacts is exactly that in the picture, I'm 100% sure they are not silver.
I don't know anything else, except that they souldn't be black.
Vinegar to remove the oxid doesn't seem a bad idea, if it doesn't work it's easily washable from the contact surface, so i guess I'll give it a try...
You really don't want to be creating any particles or additional microscopic scratches on the contacts. The leaf contacts have sufficient pressure to maintain cleaning action. You just want something to keep the oxidation under control (so you don't have the exercise the switches too often to mechanically self-clean them), Vaseline works well for that.
But vaseline doesn't remove the oxide, right? It justs makes everything smoother, but no really cleaning and deoxiding action, which is what i'm looking for
It's pretty soft, I can't see it damaging even the the most "woke" of metals, but cleans oxidation off really well without scratching.
It's excellent at restoring unobtanium switch contacts.
Only drawback is you tend to get microscopic glass fibre splinters in your fingers.
Very annoying.
Well, i may try it, at this point i'm open to every possible solution...
I think it's a mistake to use chemicals. I would, instead, polish the surfaces until the oxide is gone.
Many a decade box has been ruined by various chemicals. Alcohols, reducers, lubricants. Especially for low resistance boxes. High quality switches are not enclosed and cleaning is possible.
Probably what i'll try before anything else, thanks!
For circuit board contacts (fingers), I have used denatured alcohol. I'm told that they add a small amount of kerosene to "denature" the alcohol to stop people from drinking it. The alcohol soon evaporates but it seems to leave a very small amount of oily film (kerosene?) on the contacts and I notice that the boards slide in and out of the connectors much easier and seem to make more reliable connections.
I think that WD-40 is also mostly kerosene but with some drying agents added. So it might work just as well.
It doesn't remove the oxide tho, so the wiper still contacts the oxide and not the clean surface