Good evening.
Some background.
My computer did not turn on last yesterday, at all. some fans worked dome didn't. I ordered a replacement motherboard and a replacement CPU.
After swamping the MB with the old CPU, the PC came back to life, however my WD60EZAZ-00ZGHB0 is no longer recognized by the BIOS.

I tried another PC and the drive makes no sound, no vibration... nothing. This is the 6 TB version and I had on it quite a lot of critical documents, that I don't want to lose.

So the desperate google search leads me to this forum, which it is my last hope to get my data back.

So I have a couple of questions.
First is I'm guessing purchasing a replacement board, in this case it will be a "2060-800077-003" but I'm reading there are two versions, an unlocked, and an locked version. What is the difference?
I read that you need to remove the old bios chips. (3 on this board) and put them on the new donor board

So what do I do? do I buy an unlocked or unlocked board and is https://www.hddzone.com/ a good source for this?
Would that be the first step?

Check the TVS diodes and fuses.

TVS Diode FAQ:
http://www.hddoracle.com/viewtopic.php?f=100&t=86

... or upload a photo and I'll show you what to test.

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A backup a day keeps DR away.

Professionals buy unlocked boards to enable them to work with the drive's firmware.

In your case, the drive should not have a firmware problem, since the problem should be relegated to just an electronics issue (hopefully internal preamp chip isn't damaged).

HDDZone is ok, along with fzabkar's advice to try out first.

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Hard Disk Drive, SSD, USB Drive and RAID Data Recovery Specialist in Massachusetts

The drive is an SMR model, so 2 of the 3 "ROMs" may be nonvolatile cache for power loss protection. If so, then I would think that all 3 chips would need to be transferred, otherwise there may be a risk of contaminating the patient's data with the donor's cache.

https://hddscan.com/blog/2020/hdd-wd-smr.html

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A backup a day keeps DR away.

here is the electronic picture

This is an MCU locked drive, so transplanting the ROM to another PCB won't help. Buying an unlocked PCB isn't going to help an end user, because it only allows access to the firmware -- the actual data will be still encrypted.

Your best bet is to repair the original PCB.

If the MCU is damaged, you are out of luck.

This is the current trend for WD security. Right now bad MCUs mean unrecoverable data, unless there is a copy of the key somewhere on the platter or ROM, that is not also encrypted . . .

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http://www.datasaversllc.com

Check the TVS diodes and fuses.

TVS Diode FAQ:
http://www.hddoracle.com/viewtopic.php?f=100&t=86

_________________
A backup a day keeps DR away.

The OP's model is the subject of a law suit:

Western Digital Lawsuit For Shipping Slower SMR Hard Drives Including WD Red NAS:
https://www.hattislaw.com/cases/investigations/western-digital-lawsuit-for-shipping-slower-smr-hard-drives-including-wd-red-nas/

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A backup a day keeps DR away.