There are a couple of things that might be causing your problem. The first thing to consider is that over time, the ram could have unseated. I believe that older macs will sound long tones whenever they detect an issue with RAM upon startup. Another thing to consider is that these machines are notorious for having capacitors on their motherboard that go bad over time and swell up/leak. I would recommend taking the computer apart and reseating the RAM. While you're at it, check all of the connections from to and from the motherboard and also inspect the capacitors. iFixit doesn't have a disassembly guide for the SE/30 but [http://www.biwa.ne.jp/~shamada/fullmac/repairEng.html|this webside] give a pretty good description and also offers some troubleshooting procedures. I can't stress how important it is to carefully follow the CRT discharge procedures highlighted on the site before doing any other work on the Macintosh. [http://www.tnpcnewsletter.com/dan/Bulging_Capacitors/close-up.jpg|This picture] gives a pretty good description of what bad capacitors look like also. If you see anything suspicions, feel free to post pictures and I'll give you any input I can.