The traditional "WD-40" in a blue and yellow can is mostly kerosene. It's a water displacer and is marketed to do many things, none of which it does as well as a specialized product. It won't hurt a PCB, but it will make an oily mess, fortunately it's fairly easy to wash off. Those rust dissolving products do work well, I use one called Evaporust which works remarkably well, you just put the item in a pan or a ziplock freezer bag, pour some in and let it soak for a day or two. A soft brass bristled brush is also good for cleaning up this sort of thing. Once finished, shoot it with a coat of conformal coating or clear lacquer to prevent future corrosion. That board doesn't look too bad at all to me, it will clean up fine.
Thank you. Looks like a nice product. I'll be looking for it and for the WD-40 "specialist rust remover" locally.
For preservation, I'm already looking into conformal coating and lacquer. I'm not sure what type to get still. Conformal coating is not available locally, so I have to import it.
Importing aerosols can be troublesome because air couriers just won't let you ship those. Also, large containers of chemical products will definitely call their attention.
My only hope is liquid conformal coating, in a very small presentation. I've found several of those on Amazon, but I'm not sure how nice the finish will be on the PCB. After all, I'm brushing shinny stuff on a PCB. I think I will get a variant that can be removed with isopropyl alcohol, just in case it looks horrible.
I think I will display the board and the whole project. I will reassemble it as it was. The enclosure will be a "display box". It will consist of a wooden board that supports the kit, just like before, but this time larger. A small panel on the rear will give access to the power and audio connectors. An acrylic box will be placed on top of the wooden board to protect the whole project.
Something like this:
The acrylic box will be shaped in such a way that it accommodates the rear panel. This way I don't have to unplug anything when I want to put the acrylic box back on the project.
I managed to desolder the tube sockets. There is some corrosion in those. It has some blue or green deposit that looks like it could be some sort of salt. I wonder if it's copper with something else.