Mattis Lind from this forum sent me some failed National Semiconductor 74xx series, plastic encapsulated. These were from an HP 98xx series calculator I believe. He noticed than when they failed they failed open. I failed myself to have the local National Semi people interested in looking at them, and I just did some XRays to find out if something obvious had happened to the wire bonds. Nothing we could see, but we didn't take enough close ups. I want to take a look again, and if I don't find anything could send them on to you if Mattis is OK with it. Marc why