My 3458A tested with marginal RAM when I sent it to Loveland for cal. Gary advised that I buy the replacement RAM board which uses RAM chips that have replaceable batteries (? could they be super caps?) that snap onto the tops of the chips. They sent the meter back to me with no charge other than for shipping. I bought the upgrade board and new cable which is needed because the new board is shorter than the old style, and the old cable won't reach. Then I sent it back to Loveland for cal. I think the RAM board was around $450 -- old memory in failing RAM chips in head.... bad batteries there too. Dick Moore