I'm a long-time HP calcaholic and just getting started now buying and restoring Classic series calcs. Befroe starting my first project (a pretty sad HP-55) I read up everything on this site and elsewhere. I was able to get the dead 55 running in just a few minutes (a broken trace - I am an EE so this is my area of expertise), much to my delight. The keyboard and display work perfectly, so "all" that was left was the cosmetic restoration. In the mean time I'm using it as my daily calc and LOVING it.
After complete disassembly I prepared to wash the case halves in a diluted 409 solution. After soaking in the solution for just a few minutes, I pulled out the case top and to my HORROR several of the pad-printed legends (gold/blue) were dissolving away!!! I've not read this anywhere? Previously the letters were in GOOD shape. not all of them dissolved, but now it looks really shabby :-( My long term intent is to create a new overlay (if successful I will post here).
Has anyone else seen this problem? I'm getting 3-4 other Classics ready for restoration, but I'm really nervous about this step.
Mark