I recently brought a Stars to life that had an MPU that had been exposed to 12vdc instead of the 5vdc it's supposed to get... It fried quite a few of the chips that are not able to tolerate more than 5vdc. In your case (mine was an mpu-100, yours is an mpu-200 which is a little different) that would appear to (possibly) include the ram chips at U7, U8, and U13 (2x 5101 and 1x 6810), the clock chips at U15+U16 (9602 & 3459). My ROMs survived, and it's possible your roms, pias, and cpu/6800 *might* have survived, though they have low voltage tolerances like those other chips. Not to say you're gonna have to replace all those chips, but that's what it took in my case.
Using a logic probe, it's possible to test the chips and determine what might be fried.