Update. This is a good one. I ended up replacing the Bourn filter RP2 with a replacement I plucked from a dead SE/30 board (my first experiment with replacing the caps a couple years ago...) pretty much like Phreakout described. Excruciating process, took me a good hour just to extract it. It turned out not to help my simasimac problem unfortunately. At this point I was ready to give up and started browsing ebay for a replacement. Then I recalled a number of posts on the web about putting the motherboard in the dishwasher. I had nothing to lose but a couple of drops of dish soap, and it was a good way to pay my last respects to my SE/30... I washed the board carefully in soap water with a toothbrush and spend the next 12 hours hair drying it and blowing canned air at all angles every hour until dry. I mounted the board back in place, turned the power on and -- mirabile dictu -- the Mac showed me a nice uniform gray screen and started booting!! Unbelievable. There was no obvious trace of gunk on the board but a good clean up apparently took care of some bad contacts somewhere. I have been using the Mac for several hours since and it works fine. I did get an occasional 4-tone chime with the zebra stripes, but it might be because I didn't solder the RP2 (I just plugged it and bent the legs over the grommets for contact, traumatized by the idea of having to desolder it back). In any case that is great progress. Hope this story can be helpful to someone.