HP-67 1705A1636 very bad oxidation looking for suggestions

[[kby]]

Cleaning: that looks more like rust (iron oxidation) rather than most of the material for the calculator. I might try a fiberglass circuit board prep pen on some if that. Do it over a trash can or the broken fiberglass gets everywhere (itching powder). This looks like the kind I use:

https://www.autobodytoolmart.com/product...acQAvD_BwE

I might start with something other than the recording head. Some solvent like alcohol and a soft cloth with some gentle rubbing will hopefully remove the stuff as it doesn’t look like it came from the head itself. Same may work for some other areas you can get to and support whilst cleaning.

Repairing traces: depends on the extent. The stuff here:

https://www.soldertools.net/categories/P...Materials/

Can, I think, theoretically do a nice job. However their older method with the epoxy leaves the trace hard to redo if you make a mistake. They have some new dry film adhesive stuff that looks more promising but I haven’t tried yet. This is particularly important because we usually have multiple fine and close together traces that are damaged in the corroded area an I find the epoxy method very hard to do in that kind of situation. So, I think this is a good idea but I can’t actually say I’ve had more than limited success. Wires are easier, but this has the potential to look nicer with practice. But it’s not that cheap either. And it works best if the area to be reconstructed is straight. I haven’t found a good way to do custom bends cleanly.