Ayup, Standard DeclROM on EPROM replaced by EEPROM = OVERLY Expensive to be a Production Part = Hacked DeclROM suspicions.

Apply compressed air, maybe even remove controller PCB & wash . . . YUCK!!!!!!!!!!!!!!!! 8-o

DO NOT mess around with anything DIRECTLY attached to the platters/heads enclosure. The nut probably retains the axle on which the heads operate and those cooling vanes have sucked a friggin' crapload of dust in between the Controller PCB and Mechanism Casing!