500GB External My Book (Suspected burnt PCB)

Model number on external drive case is WD5000I032.

Model on hard disk is WD5000AJB Caviar SE.

The drive ejected from my system last night and the circle case light started blinking.  I removed the hard disk and put it in another external case but the drive itself is not spinning.  After reading some things on here, I suspect the PCB is burnt.  

I have a lot of data on this drive that I really want to salvage.  I would really appreciate any help anyone can give me.

Here is a picture of the PCB:

I removed the 12V TVS diode and it is working again, save for the original WD power supply, I have it in an alternate external case now.

How at risk is the HD from over-volting without a replacement TVS diode/can anyone direct where to find the proper replacement?