The HP power cord stocked by Allied Electronics is Volex part number 17952 8 B1, and Allied's stock number is 626-3569 at $ 9.75 each. The center contact is ground, as it should be. The description and datasheet are found here: <www.alliedelec.com/search/productdetail.aspx?SKU=6263569> 73, Eric Lemmon WB6FLY