From: ethan+@pitt.edu Subject: IIsi speaker contacts: the last word! Greetings all- After offering some (apparently mistaken) advice on how to clean up the speaker contacts on the IIsi, I received the following note from Mike Strange. It seems that he knows what he is talking about! He gave me permission to publish it here. Ethan Benatan ethan+@pitt.edu http://www.pitt.edu/~ethan ============================ Mike Strange's advice on cleaning copper contacts ------------------------------------------------- From: strange@ping.at (Mike Strange) Subject: Contacts Regarding your post about your si speaker contacts, I have a little experience with a similar contact problem. And the solution that we found may help you. A little background: I used to work as an engineering contractor to the Navy and we were forever having problems with board contacts going bad in the computers. We tried the logical thing and sanded them every time we could, but as you know, that is only good for about a week. Much less in an ocean environment. Anyway, we studied it a little and found that the sandpapering was actually accelerating the corrosion process. One reason was that there were little tiny particals of sand that remained imbedded in the surface of the contact, providing a nucleation point for corrosion. Second was that the groves left by the paper itself (600 grit) were great nucleation points also. We were actually making it worse (A classic example of Deming's tampering theory). In addition, after a couple months of sanding, there isn't much contact left. The solution was to just remove the corrosion with something less abrasive. Namely, a pink pencil eraser. The white ones aren't agressive enough. An old Dixon pencil is your best friend in these situations. We found that treating with the eraser was almost as good as having a new board. Treating with the eraser, after they had been sanded didn't really help that much because the abrasive sanding particals were still in the contact. The final trick was to apply just a thin coat of Vaselline (I can't spell it right, you know what I mean.) When I mean thin, I mean thin. That gave the best performance of all. Hopefully somewhere some of those boards are still running. Good luck. -Mike Michael Strange strange@ping.at