Hi,

I'm in the process of trying to fix the SCSI on my SE30 as well, and found the original circuit diagrams incredibly useful (but that hasn't lead to any success yet ).

Don't know if you have them already but I found them here:

http://cdn.preterhuman.net/texts/computing/Apple_Schematics/SE-30%20-or-%20IIcx%20without%20NuBus/

Best of luck and I hope you get it sorted.