I also do refurbishing, I’ve never found IPA to damage boards (evaporates fast without any residue.)
You can deyellow with retrobright, but the downside is that it makes plastic more brittle. If the plastic is already brittle, there’s not many options that don’t involve melting/warping the plastic. For some stains you can get them out with a magic eraser, it’s essentially a high grit sponge.
Agreed about deoxit, it’s still good for contacts though (cartridges and such.)
You can deyellow with retrobright, but the downside is that it makes plastic more brittle. If the plastic is already brittle, there’s not many options that don’t involve melting/warping the plastic. For some stains you can get them out with a magic eraser, it’s essentially a high grit sponge.
Agreed about deoxit, it’s still good for contacts though (cartridges and such.)