I couldn't find a thread already discussing this problem, but if there is please direct me to that one and I'll delete this one.
First off, when referencing the circuit board on an external harddrive bridging the psu and usb cables, is it controller or chipset? (I'll just call it chipset untill I'm corrected).
I recently purchased a Western Digital Elements 2 TB and about a week ago I managed to accidently knock it off my desk. It showed no signs of damage and still worked fine. That is until today when I tried to plug it in, nothing happend. I tried un- and in-plugging the PSU and the light indicator briefly turned on, I tried different mini-usb cables and a different PSU from an earlier WD Elements I had. No matter what I tried, it wouldn't turn on.
Then I opened the casing it was in to look for any damages there, but couldn't indentify any. Thats when I tried switching the chipset of the WD Elements 2 tb with the WD El. 1 tb I still had lying around and it worked. I could read all the files, store and copy off and has now worked for a good hour.
The only thing I'm concerned with right now is if it's dangerous to swap chipsets like this? Are the chipsets made specificaly for the hd size they are used for and am I putting an enormous stress on the WD El. 1 tb chipset?
There are no electrical issues, so your PCB swap will be OK. In fact your drive should work in most third party enclosures.
Just be aware that some WD models (eg Essentials) incorporate 128-bit AES hardware encryption, so a board swap will fail in those cases. Furthermore, current 3TB My Books use 4KB sector sizes whereas your EHDD would use traditional 512-byte sectors, so a board swap would fail in such cases also.