I'm having an issue with a Workcentre 7845 not completeing the alt boot. It get to network controller and checks that off but never starts with copy controller, print/copy engine or scan engine. The post code is u with flashing decimal. Procedure says to replace hard drive which I have, and then sbc pwb which I've also replaced. Still having the same issue. Spoke with a Xerox hardware engineer who told me to replace the dimms on the board. Replaced both sets. Still having the same issue. Any ideas?