Randy, 'quarks' is another volt-nuts companion. His instrument is from 1989, and we both changed all nvSRAMs in our 3458As. The complete designations are: DS1220AD-150+ and DS1230Y-150+. If the 1230 battery fails, you will get failure messages on booting the 3458A, and your stored settings and key function definitions will be lost, so that's a bit uncomfortable at most. Frank