Can a hdd circuit be replaced

In theory, you can replace the circuit board by physically removing the circuit board and replacing it with an identical rev from the same model. In most cases, you will have to move a chip from the old board to the new; this chip contains geometry information for the particular drive that was written during manufacturing.

If you search this forum for the subject, you will see posts from some drive experts who have actually done this.

Rant: Sorry, I don't believe in it. In almost all cases, that is not the source of the problem. I would run a few recovery apps (EASEUS partition recovery, Recuva, any of the dozen referenced in this forum) before trying that, if the BIOS can see the drive.
End rant. This rant is based on my personal experience; more experienced professionals think otherwise.

Can you try popping the HDD in an external enclosure, connect it to another (working) PC and see if it is recognized?

I think I was mistaken when I stated the bios recognized the HDD. I believe what i was seeing was a generic message (which I saw on unused SATA slots). I removed the PCB and found a small brown spot on the cusion facing the firmware chip. No information seeme to be going too or coming from the HDD. One tech at WD said replacing the board with the same model won't work and another said it should. Not sure what to believe but thanks for your input. George

I'm no expert, but the data recovery professionals at HDD Guru will all tell you that the chances of a successful board swap in a recent model WD drive are very slim. To guarantee success, you need to move the "adaptive" data from patient to donor. These data are stored in flash memory on the PCB, either in a separate IC at location U12, or within the Marvell MCU itself.

Could we see some photos?

If you install the drive's PM2 jumper (Power Up In Standby), does the drive then appear in BIOS? When PUIS is enabled, the drive identifies itself with the information stored in the flash memory chip. Otherwise, if PUIS is disabled, the drive spins up and attempts to use the Identify Device data stored in a hidden System Area (SA) on the platters.

BTW, if a drive spins up, then its PCB is most probably OK.