First things first, the PRAM battery on the logic board needs to be pulled, rather now than tomorrow, because they can explode and throw extremely corrosive battery goop all over the circuit board, which will quickly destroy it.
It is even possible that that has already happened, and this is the result.
If it hasn't happened yet, at minimum the Mac will need a recap, the SMD capacitors on the logic board of an SE/30 will always catastrophically leak electrolytic fluid that is corrosive to the circuit board.
After that, it's not unlikely that some of the chips in the video circuitry (74 logic chips such as UE8, UF8, etc.) have died from having that fluid corrode them to the point of failure.
It's sadly not an easy fix, but someone with enough board repair skills could fix it if it isn't too catastrophic.
Even then, there is an open source logic board recreation by
@Bolle, meaning the custom SE/30 chips that survived could be transplanted to a fresh board, to give the SE/30 a second chance at life.
In any case, it's good you saved it from its fate, as even the worst condition SE/30s can still go a long way with repairs, or the logic board replica.
