I would be tempted to take a board ot two outside and then use compressed air to get off as much as possilble that way first, before cleaning with anything. Bill
On Sun, Apr 23, 2023, 12:54 PM Fritz Mueller via cctalk < [email protected]> wrote: > Hi folks, > > I’ve been picking my way through a PDP-8/L restoration lately. I’ve found > that everything in the machine is covered with a uniform layer of dark > “soot” (enough to blacken your hands while working with it) which I would > like to clean up. Perhaps the “soot” is actually from a decomposed air > filter, as I don’t imagine this machine was operated in a smoky > environment, and there is no smoke odor. > > I usually use 99 IPA and cleanroom wipes for spot cleaning these sorts of > things, but in this case there is so much of it that I feel that would just > push the soot around rather than clean it off. I think some sort of actual > rinse would be needed here. > > I’ve been eying the dishwasher, for the subset of flip chips that that are > just DIP logic, carbon comp resistors, and ceramic bypass caps, anyway. > But I haven’t been brave enough to try that yet... Most of the logic here > has date codes to ’68 or ’69, so I’m inclined to treat it gently. Any > suggestions for approaches to clean this up? > > Follow-on question: the majority of the legs on these old DIPs are showing > what I’d call “moderate” corrosion — nothing looks like it is in danger of > being eaten all the way through, but the process is underway. I was > wondering if something like a light shellac or other inhibitor could be > brushed over these pins to at least slow their inevitable demise? > > I did purchase and build out one of Vince’s flip chip tester kits, and > have found it super useful for this project. Of the large percentage > modules that have test vectors supplied, most have tested fine. Three M216 > flip-flop modules and one M113 nand module were flagged for repairs this > way. > > Advice appreciated, as always! > > cheers, > —FritzM. > > >
