Hitachi HTS725050A7E630 ARM Family, corrupted NVR

[Powermax]

Hi to all, i have this Hitachi Hdd with PCB problem, infact if i read NVR more times, save it in more files and after i compare it, i can see are all different. I have unsoldered patient NVR and i solder it on donor PCB. I try to read more time NVR like before, and now all files are ugual. I suppose patient PCB have somo problem on read channel of processor. After i used donor pcb with patient nvr on Hdd, now Hdd start motor but i can ear heads knock. Now i swapped heads with good ones, but hdd knock the same. I suppose patient NVR have corruption on code. I need to know if there are some way to obtain a NVR code copy from SA and if yes how i can do that.
Thank you to all.