Little Update:
i've found a compatible pcb and i've swapped the NVRAM chip, the disk is alive!
i've recovered the files i needed, a few gbs with an external ide to usb cable, powering the hdd with a standard atx psu (the external little thing they gave me with the cable wasn't stable enough).
so, i can tell that in this case, searching for a donor pcb, with the same:
-p/n number, on the disk label
-MLC Number, on the disk label
-first two line of the pcb number, on the pcb label, above the ide connector
-same assembly place (made in china in my case)
-max 30 days between the production date
in my particular case
-the motor controller was different,
-the main controller has the same first line number 47P2010 but the second numerical line was different for the last third digit (original was: 1J06T02MLQ donor was: 1J06T02QLQ)
-the other big component, i think is the memory, but i'm not sure, is different:
DONOR:__________ORIGINAL:
IBM______________IBM
TAIWAN__________TAIWAN
SPRCBM BB_______SPRCBM BB
50G7143__________50G7143
1F10076TQT_______1J14002TQT
WELL,
i don't really know if i was lucky (for the first time ever) but i can say that, IN MY CASE, the pcb swap, with nvram swap, has worked.
thanks everyone for the help and the suggestions
bye
giorgio