Can you replace the circuit boards on an external hard drive?

Gary, the only thing that you could try is to get a PCB from the same model and replace it. This may enable you to access your drive. However, the larger drives do have some issues with that. If it is important data that you have on the drive, you may consider a data recovery service$$$ or some electronic repair shop that might fix it for you $$. There is some great discussion about an issue like that on here. Hope this helps, good luck.

i found one for you at http://pcb-hdd.com/wd30ezrs-11j99b0-2060...

"http://www.hddzone.com/wd-2060771698002-...

I found this pcb supplier, cheaper with free shipping."