I have a software RAID-5 array of 4 Toshiba DT01ACA200 HDDs working on Storage Spaces on Windows 10.

First HDD failed a week ago and because of some neglecting a second HDD failed after three or four days, they were not spinning at all
After digging, the problems were on the PCBs and they were not identical.
I checked TVS diodes , they were fine
Take a look on the attached file (PCB in the attachment is the same i had on those HDDs but it is from google, not mine ) After opening the borads , the first one had a broken fuse (Arrow No.1 ) , and the second board has fried cooked transistor (Arrow No.2).
we checked the same transistor on the other board , it looks clean but no it is not , it is broken too but no high temperature traces are left.

I do have a backup but restoring it can cause me up to 60 days of work , so it is a final option for me if i can't repair the HDDs

Sorry that I'm new to this type of problems and to this forum too your help can get in handy very much, what are the available solutions to repair the HDD,
* can i just replace the transistor from another PCB ?
* I read that replacing the WHOLE PCB is not an option for new drives because of some firmware, is that true?
* Can i replace the whole PCB and in the new PCB put the ROM that contains the firmware from the old PCB ?

I hope you can suggest some solution for my problem.
PS: Sorry for my bad Engilsh