On Tue, January 19, 2016 5:29 pm, J Martin Rushton wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > I suspect that the gold layer on edge connectors 30-odd years ago was > a lot thicker than on modern cards. I remember a long time ago - that actually was in the country "Far -Far Away" ;-) We were not allowed to dispose of connectors with gold plated contacts. These were collected, and gold was extracted from them and re-used. I believe, there were dissolving base brass material with acid, then just melted the thin gold shells left. Not useful with modern super thin plating. > We are talking contacts on 0.1" > spacing not some modern 1/10 of a knat's whisker. (Off topic) I also > remember seeing engineers determine which memory chip was at fault and > replacing the chip using a soldering iron. Try that on a DIMM! > > On 19/01/16 00:39, Peter wrote: >> On 19/01/16 12:34, J Martin Rushton wrote: >>> Not new: I can remember seeing DEC engineers cleaning up the >>> contacts on memory boards for a VAX 11/782 with a pencil eraser >>> c.1985. It's still a pretty standard first fix to reseat a card >>> or connector. >> >> I used to do that as well. The contacts would come out nice and >> shiny when you clean them. Then I found out that what I was >> actually doing was removing the very thin layer of gold plating on >> the contacts and revealing the copper underneath. That's why you >> should never clean contacts with a pencil eraser, just re-seat the >> boards and they'll make contact again. >> ++++++++++++++++++++++++++++++++++++++++ Valeri Galtsev Sr System Administrator Department of Astronomy and Astrophysics Kavli Institute for Cosmological Physics University of Chicago Phone: 773-702-4247 ++++++++++++++++++++++++++++++++++++++++