The NVRAM on the PCB lost its configuration (or you swapped a PCB from a donor drive). Without the correct "ROM" data, the drive won't initialize the heads.
MRT is a cheaper competitor to PC-3000 (starting around $1,500). Their Hitachi module is surprisingly powerful. hitachi hdd repair tool
Can attempt to rewrite or "zero out" bad sectors to make the drive usable again. Victoria HDD The NVRAM on the PCB lost its configuration