If you hadn't mentioned that your fan wasn't spinning, I would have suggested you swap out the logic board. But if the fan isn't spinning and now that you have confirmed all is well with the PSU, clearly your analog board is suspect.
Page 149 of Larry Pina's excellent The Dead Mac Scrolls talks about an SE/30 with no startup bong, black display, completed dead (no fan or other noise). But it suggests the problem in this case is likely the Sony PSU. Then on page 50 it talks about a case where the fan and hard drive spin but everything else dead, in which case it suggests replacing R22 (470k-ohm 1/2W 5%) on the analog board. Those are the only two cases in the entire book that closely resemble your description, unfortunately.
If you had another known-good SE/30 you could swap out things one by one to ultimate determine the root problem. But it would appear that you lack such parts. But if you are in the US, then it wouldn't cost much to purchase something like off EBAY. For me in Japan, now that USPS no long does ocean/surface mail, such would be impossible. I'm glad I ordered my vintage Mac systems when I did, at a time shipping from the US to Japan was reasonable!
Page 149 of Larry Pina's excellent The Dead Mac Scrolls talks about an SE/30 with no startup bong, black display, completed dead (no fan or other noise). But it suggests the problem in this case is likely the Sony PSU. Then on page 50 it talks about a case where the fan and hard drive spin but everything else dead, in which case it suggests replacing R22 (470k-ohm 1/2W 5%) on the analog board. Those are the only two cases in the entire book that closely resemble your description, unfortunately.
If you had another known-good SE/30 you could swap out things one by one to ultimate determine the root problem. But it would appear that you lack such parts. But if you are in the US, then it wouldn't cost much to purchase something like off EBAY. For me in Japan, now that USPS no long does ocean/surface mail, such would be impossible. I'm glad I ordered my vintage Mac systems when I did, at a time shipping from the US to Japan was reasonable!